Information processing device

ABSTRACT

A novel information processing device that is highly convenient is provided. The information processing device includes a selection circuit having a function of supplying image data to a reflective display element, a light-emitting element, or both of them on the basis of input position coordinate data, sensing data about the illuminance of the usage environment, and the image data. An icon with high selection frequency is displayed by both the reflective display element and the light-emitting element on the basis of icon coordinate data and the input position coordinate data, so that the icon can be displayed brightly with improved visibility.

TECHNICAL FIELD

One embodiment of the present invention relates to an informationprocessing device or a semiconductor device.

Note that one embodiment of the present invention is not limited to theabove technical field. The technical field of one embodiment of theinvention disclosed in this specification and the like relates to anobject, a method, or a manufacturing method. Furthermore, one embodimentof the present invention relates to a process, a machine, manufacture,or a composition of matter. Specifically, examples of the technicalfield of one embodiment of the present invention disclosed in thisspecification include a semiconductor device, a display device, alight-emitting device, a power storage device, a memory device, a methodfor driving any of them, and a method for manufacturing any of them.

BACKGROUND ART

A liquid crystal display device in which a light-condensing means and apixel electrode are provided on the same surface side of a substrate anda region transmitting visible light in the pixel electrode is providedto overlap with an optical axis of the light-condensing means, and aliquid crystal display device which includes an anisotropiclight-condensing means having a condensing direction X and anon-condensing direction Y that is along a longitudinal direction of aregion transmitting visible light in the pixel electrode are known(Patent Document 1).

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2011-191750

DISCLOSURE OF INVENTION

An object of one embodiment of the present invention is to provide anovel information processing device that is highly convenient. Anotherobject is to provide a novel information processing device or a novelsemiconductor device.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all of these objects. Other objects will be apparentfrom and can be derived from the description of the specification, thedrawings, the claims, and the like.

One embodiment of the present invention is an information processingdevice including an input/output device and an arithmetic device.

The input/output device is configured to supply input positioncoordinate data.

The arithmetic device is configured to receive the input positioncoordinate data. The arithmetic device is configured to supply imagedata and control data.

The input/output device includes a display portion and an input portion.

The input portion is configured to supply the input position coordinatedata. The input position coordinate data is data on coordinates in onedisplay portion.

The display portion is configured to display the image data.

The display portion includes a selection circuit, a first drivercircuit, a second driver circuit, and a display panel.

The arithmetic device includes a memory portion and is configured tostore icon coordinate data including data on coordinates whereindividual icons are displayed in the display portion and selectionhistories of the icons. In this specification, an icon refers to afigure or an image associated with a command for executing a program orthe like. For example, a user of the information processing device caneasily execute a predetermined command by selecting an icon with apointer or the like. The icon may be dragged, moved, or placed on thedisplay screen. The icon spreads over a certain range. In other words,each icon coordinate data includes data for all the area of this icon.

The arithmetic device is configured to determine whether there is anoverlap between the input position coordinate data and the iconcoordinate data. The occurrence of an overlap between the input positioncoordinate data and the icon coordinate data is described as “theselection of an icon”, and this icon is described as “the selectedicon”.

Furthermore, the arithmetic device is configured to generate the imagedata.

Moreover, the arithmetic device is configured to generate the controldata, which is the data varying depending on the coordinates in thedisplay portion. The control data is set to be any of a first-statuscontrol data, a second-status control data, and a third-status controldata.

The arithmetic device generates the third-status control data when aparticular input position coordinate data is supplied.

The selection circuit is configured to supply the image data to thefirst driver circuit or the second driver circuit when the first-statusor second-status control data is supplied from the arithmetic device. Atthis time, the image data is supplied to one of the first and seconddriver circuits, and background data is supplied to the other thereof.The background data is data for displaying a black image.

The selection circuit is configured to supply the image data to both ofthe first and second driver circuits when the third-status control datais supplied from the arithmetic device.

Here, when a certain image data is generated by the arithmetic deviceand displayed in the display portion, the luminance of the displayportion when the third-status control data is supplied is higher thanthat of the display portion when the first or second status control datais supplied. In this manner, the luminance can be increased and visualemphasis is possible in the display mode selected on the basis of theinput position coordinate data obtained from the input/output device.Thus, a novel information processing device that is highly convenientcan be provided.

The information processing device of one embodiment of the presentinvention is configured to store the number of times the icons areselected in the arithmetic device on the basis of the input positioncoordinate data obtained from the input/output device. A threshold valueis set, and the third-status control data is supplied for the icon whichis selected more than (i.e., with a higher frequency than) the thresholdvalue. Thus, the icon with high selection frequency can be visuallyemphasized in the information processing device.

In one embodiment of the present invention, the input/output deviceincludes a sensor portion configured to supply sensing data. Thearithmetic device is configured to receive the sensing data. The sensorportion includes an illuminance sensor in the information processingdevice.

The illuminance sensor is configured to supply the sensing dataincluding illuminance data on an environment where the informationprocessing device is used.

The information processing device of one embodiment of the presentinvention includes the arithmetic device which is configured todetermine the status on the basis of the sensing data and the image dataand supply the control data in the determined status. In other words,the arithmetic device is configured to determine the luminance of thedisplay when the image data is supplied to the first driver circuit andthe display when the image data is supplied to the second drivercircuit, on the basis of the supplied sensing data. Thus, a reflectivedisplay element or a light-emitting element is selected on the basis ofthe sensing data on illuminance or the like and the image data, and theimage data can be displayed using the selected reflective displayelement or light-emitting element. As a result, a novel informationprocessing device that is highly convenient can be provided.

Although the block diagram attached to this specification showscomponents classified by their functions in independent blocks, it isdifficult to classify actual components according to their functionscompletely and it is possible for one component to have a plurality offunctions.

In this specification, the terms “source” and “drain” of a transistorinterchange with each other depending on the polarity of the transistoror the levels of potentials applied to the terminals. In general, in ann-channel transistor, a terminal to which a lower potential is appliedis called a source, and a terminal to which a higher potential isapplied is called a drain. In a p-channel transistor, a terminal towhich a lower potential is applied is called a drain, and a terminal towhich a higher potential is applied is called a source. In thisspecification, although connection relation of the transistor isdescribed assuming that the source and the drain are fixed forconvenience in some cases, actually, the names of the source and thedrain interchange with each other depending on the relation of thepotentials.

Note that in this specification, a “source” of a transistor means asource region that is part of a semiconductor film functioning as anactive layer or a source electrode connected to the semiconductor film.Similarly, a “drain” of a transistor means a drain region that is partof the semiconductor film or a drain electrode connected to thesemiconductor film. A “gate” means a gate electrode.

Note that in this specification, a state in which transistors areconnected to each other in series means, for example, a state in whichonly one of a source and a drain of a first transistor is connected toonly one of a source and a drain of a second transistor. In addition, astate in which transistors are connected in parallel means a state inwhich one of a source and a drain of a first transistor is connected toone of a source and a drain of a second transistor and the other of thesource and the drain of the first transistor is connected to the otherof the source and the drain of the second transistor.

In this specification, the term “connection” means electrical connectionand corresponds to a state where a current, a voltage, or a potentialcan be supplied or transmitted. Accordingly, connection means not onlydirect connection but also indirect connection through a circuit elementsuch as a wiring, a resistor, a diode, or a transistor so that acurrent, a potential, or a voltage can be supplied or transmitted.

In this specification, even when different components are connected toeach other in a circuit diagram, there is actually a case where oneconductive film has functions of a plurality of components such as acase where part of a wiring serves as an electrode. The term“connection” in this specification also means such a case where oneconductive film has functions of a plurality of components.

Further, in this specification, one of a first electrode and a secondelectrode of a transistor refers to a source electrode and the otherrefers to a drain electrode.

One embodiment of the present invention is an information processingdevice, in which the display panel includes a first signal line, asecond signal line, and a group of pixels, the group of pixels arearranged in a column direction, the first signal line is electricallyconnected to the group of pixels arranged in the column direction, thefirst signal line is electrically connected to the first driver circuit,the second signal line is electrically connected to the group of pixelsarranged in the column direction, and the second signal line iselectrically connected to the second driver circuit.

One embodiment of the present invention is the information processingdevice, in which the group of pixels each include a first displayelement and a second display element, the first display element includesa reflective display element, the first display element is electricallyconnected to the first signal line, the second display element includesa light-emitting element, and the second display element is electricallyconnected to the second signal line.

One embodiment of the present invention is the information processingdevice, in which the first display element includes a reflective filmthat reflects external light in a display direction and is configured tocontrol the intensity of the reflected light, the reflective filmincludes an opening, and the second display element includes a regionoverlapping with the opening and a layer containing a light-emittingorganic compound and is configured to emit light toward the opening.

One embodiment of the present invention is the information processingdevice, in which the arithmetic device is configured to, when an icon isselected, supply the third-status control data to the input/outputdevice in accordance with coordinates of a region where the icon isdisplayed.

One embodiment of the present invention is the information processingdevice, in which the arithmetic device is configured to determine aparticular icon on the basis of a selection history of the icon andsupply the third-status control data toward coordinates of a regionwhere the particular icon is displayed.

One embodiment of the present invention is the information processingdevice, in which the arithmetic device is configured to supply thecontrol data in the third status toward a pointer display region until acertain period of time has passed from the last input from the inputportion, and the arithmetic device is configured to supply thefirst-status control data or the second-status control data toward thepointer display region after the certain period of time has passed fromthe last input from the input portion.

One embodiment of the present invention is the information processingdevice, in which the sensor portion includes an illuminance sensor, andthe illuminance sensor is configured to supply the sensing dataincluding illuminance data on an environment where the informationprocessing device is used.

One embodiment of the present invention is the information processingdevice, in which the input portion includes at least one of a keyboard,a hardware button, a pointing device, a touch sensor, an illuminancesensor, an imaging device, an audio input device, a viewpoint inputdevice, and an attitude determination device.

One embodiment of the present invention can provide a novel informationprocessing device that is highly convenient. One embodiment of thepresent invention can provide a novel information processing device or anovel semiconductor device.

Note that the descriptions of these effects do not disturb the existenceof other effects. One embodiment of the present invention does notnecessarily have all of these effects. Other effects will be apparentfrom and can be derived from the description of the specification, thedrawings, the claims, and the like.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are drawings for explaining a structure of aninformation processing device of an embodiment;

FIG. 2 is a flow chart showing a program that can be used in aninformation processing device of an embodiment;

FIGS. 3A to 3C each illustrate an information processing device of anembodiment;

FIGS. 4A to 4C each illustrate an information processing device of anembodiment;

FIGS. 5A to 5C are drawings for explaining image data of an informationprocessing device of an embodiment;

FIGS. 6A and 6B each illustrate a circuit of an information processingdevice of an embodiment;

FIG. 7 is a flow chart showing a program that can be used in aninformation processing device of an embodiment;

FIG. 8 is a flow chart showing a program that can be used in aninformation processing device of an embodiment;

FIGS. 9A, 9B1, and 9B2 are bottom views illustrating a structure of adisplay panel that can be used in a display device of an embodiment;

FIG. 10 is a circuit diagram illustrating a pixel circuit of a displaypanel that can be used in a display device of an embodiment;

FIGS. 11A, 11B1, and 11B2 are schematic views for explaining the shapeof a reflective film in pixels that can be used in a display device ofan embodiment;

FIGS. 12A to 12D illustrate a structure of a transistor according to anembodiment;

FIGS. 13A to 13C illustrate a structure of a transistor according to anembodiment;

FIG. 14 illustrates a structure of an input/output device according toan embodiment;

FIGS. 15A to 15C are a cross-sectional view and circuit diagrams eachillustrating a structure of a semiconductor device of an embodiment;

FIG. 16 is a block diagram illustrating a structure of a CPU of anembodiment;

FIG. 17 is a circuit diagram illustrating a structure of a memoryelement of an embodiment;

FIGS. 18A to 18H each illustrate a structure of an electronic device ofan embodiment;

FIGS. 19A to 19C are cross-sectional views illustrating a structure of adisplay panel that can be used in a display device of an embodiment; and

FIGS. 20A and 20B are cross-sectional views illustrating a structure ofa display panel that can be used in a display device of an embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

An information processing device of one embodiment of the presentinvention supplies part of image data selected on the basis of inputposition coordinate data to a first driver circuit and a second drivercircuit.

Thus, when the selected part of the image data is supplied from anarithmetic device, the selected image is displayed brightly. As aresult, a novel information processing device that is highly convenientcan be provided.

Embodiments will be described in detail with reference to the drawings.It will be readily appreciated by those skilled in the art that modesand details of the present invention can be modified in various wayswithout departing from the spirit and scope of the present invention.Thus, the present invention should not be construed as being limited tothe description in the embodiments below. Note that in structures of theinvention described below, the same portions or portions having similarfunctions are denoted by the same reference numerals in differentdrawings, and a description thereof is not repeated.

Embodiment 1

In this embodiment, a structure of an information processing device ofone embodiment of the present invention will be described with referenceto FIGS. 1A and 1B, FIG. 2, FIGS. 3A to 3C, and FIGS. 4A to 4C.

FIGS. 1A and 1B illustrate a configuration of the information processingdevice of one embodiment of the present invention. FIG. 1A is a blockdiagram of a display portion 230 that can be used in the informationprocessing device of one embodiment of the present invention and FIG. 1Bis a block diagram illustrating a selection circuit 239, a first drivercircuit SD1, or a second driver circuit SD2 in FIG. 1A.

FIG. 2 is a flow chart showing a program that can be used for theinformation processing device of one embodiment of the presentinvention.

FIG. 3A is a block diagram illustrating a configuration of aninformation processing device 200. FIGS. 3B and 3C are projection viewsillustrating examples of external views of the information processingdevice 200.

FIG. 4A is a block diagram illustrating a configuration of the displayportion 230. FIG. 4B is a block diagram illustrating a configuration ofa display portion 230B. FIG. 4C is a circuit diagram illustrating aconfiguration of a pixel 232(i, j).

<Configuration Example 1 of Information Processing Device>

The information processing device 200 described in this embodimentincludes an input/output device 220 and an arithmetic device 210 (seeFIG. 3A).

The input/output device 220 has a function of supplying input positioncoordinate data P1 and sensing data P2. In addition, the input/outputdevice 220 has a function of receiving image data V1 and control dataSS.

The arithmetic device 210 has a function of receiving the input positioncoordinate data P1 and the sensing data P2. In addition, the arithmeticdevice 210 has a function of supplying the image data V1 and the controldata SS.

The input/output device 220 includes the display portion 230, an inputportion 240, and a sensor portion 250.

The input portion 240 has a function of supplying the input positioncoordinate data P1.

The sensor portion 250 has a function of supplying the sensing data P2.

The display portion 230 has a function of displaying the image data V1.

The display portion 230 includes the selection circuit 239, the firstdriver circuit SD1, the second driver circuit SD2, and a display panel(see FIG. 1A).

The arithmetic device 210 has a function of generating the image data V1(see FIG. 3A). In addition, the arithmetic device 210 has a function ofgenerating the control data SS on the basis of the sensing data P2 andthe image data V1. Note that the control data SS is any of afirst-status control data, a second-status control data, and athird-status control data.

The selection circuit 239 has a function of supplying the image data V1to the first driver circuit SD1 and supplying background data to thesecond driver circuit SD2 when receiving the first-status control dataSS (see FIG. 1B).

The selection circuit 239 similarly has a function of supplying thebackground data to the first driver circuit SD1 and supplying the imagedata V1 to the second driver circuit SD2 when receiving thesecond-status control data SS.

The selection circuit 239 has a function of supplying the image data V1to the first driver circuit SD1 and the second driver circuit SD2 whenreceiving the third-status control data SS.

The display panel of the information processing device 200 described inthis embodiment includes a first signal line S1(j), a second signal lineS2(j), and a group of pixels 232(1, j) to 232(m, j) (see FIG. 1A).

The group of pixels 232(1, j) to 232(m, j) are arranged in a columndirection. Note that i is an integer greater than or equal to 1 and lessthan or equal to m, j is an integer greater than or equal to 1 and lessthan or equal to n, and m and n are each an integer greater than orequal to 1.

The first signal line S1(j) is electrically connected to the group ofpixels 232(1, j) to 232(m, j) arranged in the column direction. Inaddition, the first signal line S1(j) is electrically connected to thefirst driver circuit SD1.

The second signal line S2(j) is electrically connected to the group ofpixels 232(1, j) to 232(m, j) arranged in the column direction. Inaddition, the second signal line S2(j) is electrically connected to thesecond driver circuit SD2.

The pixel 232(i, j) of the information processing device 200 describedin this embodiment includes a first display element 235A and a seconddisplay element 235B (see FIG. 4C).

The first display element 235A includes a reflective display element andis electrically connected to the first signal line S1(j).

The second display element 235B includes a light-emitting element and iselectrically connected to the second signal line S2(j).

The information processing device described in this embodiment includesthe display panel including the pixel provided with the reflectivedisplay element and the light-emitting element. Thus, the reflectivedisplay element or the light-emitting element is selected on the basisof the sensing data, and the image data can be displayed using theselected reflective display element or light-emitting element. As aresult, a novel information processing device that is highly convenientcan be provided.

Furthermore, the arithmetic device 210 of the information processingdevice 200 described in this embodiment has a function of supplying thefirst-status control data SS when the input position coordinate data P1is not supplied and the sensing data P2 is greater than or equal to apredetermined threshold value.

The threshold value is, for example, the value of the sensing data P2 atwhich the same luminance can be obtained from both the reflectivedisplay element and the light-emitting element, which is obtained bychanging the sensing data P2 in the state where the reflective displayelement and the light-emitting element are individually made to displaya white image with the highest possible luminance. Alternatively, inorder to restrict image exhibition by the light-emitting element for thepurpose of lower power consumption, the sensing data P2 at the time whenthe luminance of the reflective display element is 1.5 times that of thelight-emitting element may be used as the threshold value.

Furthermore, the arithmetic device 210 supplies the second-statuscontrol data SS when the input position coordinate data P1 is notsupplied and the sensing data P2 is less than the predeterminedthreshold value.

Moreover, the sensor portion 250 of the information processing device200 described in this embodiment includes an illuminance sensor and thesensing data P2 contains illuminance data on the environment in whichthe information processing device 200 is used (see FIG. 3A).

The information processing device described in this embodiment includesthe arithmetic device which has a function of determining the status onthe basis of the sensing data and the image data and supplying thecontrol data about the determined status. Thus, the reflective displayelement or the light-emitting element is selected on the basis of thesensing data such as illuminance and the image data, and the image datacan be displayed using the selected reflective display element orlight-emitting element. As a result, a novel information processingdevice that is highly convenient can be provided.

Moreover, the information processing device 200 includes a communicationportion 290.

The following describes components included in the informationprocessing device 200. Note that these components cannot be clearlydistinguished and one component also serves as another component orincludes part of another component in some cases.

For example, the display portion 230 with which the input portion 240overlaps serves as both the input portion 240 and the display portion230.

Configuration Example

The information processing device 200 includes the arithmetic device210, the input/output device 220, the display portion 230, the sensorportion 250, or the input portion 240.

<Arithmetic Device 210>

The arithmetic device 210 includes an arithmetic portion 211 and amemory portion 212. The arithmetic device 210 further includes atransmission path 214 and an input/output interface 215.

<Arithmetic Portion 211>

The arithmetic portion 211 has a function of, for example, executing aprogram.

<Memory Portion 212>

The memory portion 212 has a function of, for example, storing theprogram executed by the arithmetic portion 211, initial data, settingdata, an image, or the like. In addition, the memory portion 212 has afunction of storing icon coordinate data.

Specifically, a hard disk, a flash memory, a transistor including anoxide semiconductor, or the like can be used.

<Program>

For example, a program for determining the status of the control data SSon the basis of the input position coordinate data P1 can be used forthe arithmetic device 210.

Compared with the image exhibition by only the reflective displayelement or only the light-emitting element, the image exhibition usingboth the reflective display element and the light-emitting elementenables a higher luminance. In an example described below, thereflective display element is used when the first-status control data issupplied, whereas the light-emitting element is used when thesecond-status control data is supplied. In addition, both the reflectivedisplay element and the light-emitting element are used when thethird-status control data is supplied.

When the third-status control data is supplied, the illuminance of thedisplay is higher than that of the display when the first-status controldata or the second-status control data is supplied, and visual emphasisis possible.

Specifically, a program including the following steps can be used.

<First Step>

In the first step, whether there is an input from the input portion 240is determined. When there is an input, the second step is selected, andwhen there is not an input, the program returns to the START state (see(T1) in FIG. 2).

<Second Step>

In the second step, the input position coordinate data P1 supplied fromthe input portion 240 is read (see (T2) in FIG. 2).

<Third Step>

In the third step, with reference to icon coordinate data supplied fromthe memory portion 212, it is determined whether there is an overlapbetween the icon coordinate data, that is, the displayed icon and theposition in the display portion designated by the input positioncoordinate data P1. When there is an overlap, the fourth step isselected. When there is not an overlap, the fifth step is selected.

<Fourth Step>

In the fourth step, the third-status control data SS is supplied towardthe position in the display portion designated by the input positioncoordinate data P1 (see (T4) in FIG. 2).

<Fifth Step>

In the fifth step, the first-status or second-status control data SS issupplied toward the position in the display portion designated by theinput position coordinate data P1 (see (T5) in FIG. 2). An example ofsupplying the first-status control data SS is described below.

In the case where an icon that is not selected is displayed, theselection circuit 239 supplies the image data V1 to the first drivercircuit SD1 and the background data to the second driver circuit SD2 onthe basis of the first-status control data SS in the process from thethird step to the START state (see FIG. 1B). In the case where an iconthat is selected is displayed, the selection circuit 239 supplies theimage data V1 to the first driver circuit SD1 and the second drivercircuit SD2 on the basis of the third-status control data SS through thefourth step and the fifth step. Then, the program returns to the STARTstate.

The reflective display element and the light-emitting element are usedin the above-described example. Depending on the pixel area or luminanceof each display element and the environment such as external light, theluminance relation might be reversed between the reflective displayelement and the light-emitting element. Therefore, the informationprocessing device 200 may have a function of appropriately changing thestatus assignment for the reflective display element and thelight-emitting element may be provided.

<Input/Output Interface 215, Transmission Path 214>

The input/output interface 215 includes a terminal or a wiring and has afunction of supplying and receiving data. For example, the input/outputinterface 215 can be electrically connected to the transmission path 214and the input/output device 220.

The transmission path 214 includes a wiring and has a function ofsupplying and receiving data. For example, the transmission path 214 canbe electrically connected to the input/output interface 215. Inaddition, the transmission path 214 can be electrically connected to thearithmetic portion 211, the memory portion 212, or the input/outputinterface 215.

<Input/Output Device 220>

The input/output device 220 includes the display portion 230, the inputportion 240, the sensor portion 250, or the communication portion 290.

For example, the input/output device 220 includes the display portion230 and the input portion 240 having a region overlapping with thedisplay portion 230. A touch panel or the like can be used for theinput/output device 220. Specifically, the touch panel described inEmbodiment 7 can be used for the input/output device 220.

<Display Portion 230>

For example, the display panel, the selection circuit 239, the drivercircuit SD1, or the driver circuit SD2 can be used in the displayportion 230 (see FIG. 1A and FIGS. 4A to 4C).

A display region 231 includes a plurality of pixel 232(i, j) to 232(i,n) arranged in a row direction, a plurality of pixels 232(1, j) to232(m, j) arranged in a column direction, scan lines G1(i) and G2(i)which are electrically connected to the plurality of pixels 232(i, 1) to232(i, n), and the signal line S1(j) and the signal line S2(j) which areelectrically connected to the plurality of pixel 232(i, j) to 232(m, j).Note that i is an integer greater than or equal to 1 and less than orequal to m, j is an integer greater than or equal to 1 and less than orequal to n, and m and n are each an integer greater than or equal to 1.

Note that the pixel 232(i, j) is electrically connected to the scan lineG1(i), the scan line G2(i), the signal line S1(j), the signal lineS2(j), a wiring ANO, a wiring CSCOM, a wiring VCOM1, and a wiring VCOM2(see FIG. 4C).

The display portion can include a plurality of driver circuits. Forexample, the display portion 230B can include a driver circuit GDA and adriver circuit GDB (see FIG. 4B).

<Driver Circuit GD>

The driver circuit GD has a function of supplying a selection signal.

For example, the driver circuit GD has a function of supplying aselection signal to one scan line with a frequency of 30 Hz or higher,preferably 60 Hz or higher, on the basis of the control data.

<Display Panel>

For example, the display region 231 which has a function of displayingthe image data V1 can be used in the display panel. Furthermore, thegroup of pixels 232(1, j) to 232(m, j) can be used in the display region231 (see FIG. 1A).

In addition, the first signal line 1(j) and the second signal line S2(j)can be used in the display panel.

Specifically, a display panel described in Embodiment 4 can be used inthe display portion 230.

<Selection Circuit 239>

In the selection circuit 239, a first multiplexer and a secondmultiplexer can be used, for example (see FIG. 1B).

The first multiplexer includes a first input portion to which the imagedata V1 is supplied, a second input portion to which the background datais supplied, and a third input portion to which the image data V1 issupplied, and receives the control data SS. The first multiplexeroutputs the image data V1 when receiving the first-status control dataSS, the background data V00 when receiving the second-status controldata SS, and the image data V1 when receiving the third-status controldata SS. Note that the data output from the first multiplexer isreferred to as data V11.

The second multiplexer includes a first input portion to which thebackground data is supplied and a second input portion and a third inputportion to which the image data V1 is supplied, and receives the controldata SS. The second multiplexer outputs the background data V00 whenreceiving the first-status control data SS, outputs the image data V1when receiving the second-status control data SS, and outputs the imagedata V1 when receiving the third-status control data SS. Note that thedata output from the second multiplexer is referred to as data V12.

The image data V1 contains signals for all the coordinates in thedisplay region 231. The signals for all the coordinates in the displayregion 231 are sequentially transmitted to the selection circuit 239.When the control data SS for certain coordinates is transmitted at thesame time when a signal for the certain coordinates among the image dataV1 is transmitted, the supply destination of the image data V1 is set toany of the following: the first driver circuit SD1, the second drivercircuit SD2, or both the first driver circuit SD1 and the second drivercircuit SD2.

In an example of an analog circuit that can be used in this embodiment,the potential of the second-status control data SS2 can be assigned as apotential higher than that of the first-status control data SS1, and thepotential of the third-status control data SS3 can be assigned as apotential higher than that of the second-status control data SS2.

An example of generating the data V11 and the data V12 from the imagedata V1 using the first-status control data SS1 and the third-statuscontrol data SS3 is described. For example, the first-status controldata can be assigned to an image that is not selected, and thethird-status control data can be assigned to an image that is selected(see FIG. 5A). Alternatively, the second-status control data may beassigned to an image that is not selected, and the third-status controldata may be assigned to an image that is selected (see FIG. 5B).

For example, the image that is selected is displayed by pixelspositioned in the (i+1)-th row and the (i+2)-th row in the displayregion 231, and the region of these pixels is referred to as a region233. Here, the arithmetic device 210 supplies the first-status controldata SS1 and the third-status control data SS3, and the selectioncircuit 239 supplies the data V11 including the image data V1 and thedata V12 including the image data V1 (see FIGS. 5A and 5C). The region233 is displayed by the image data V1 supplied to the first drivercircuit SD1 and the second driver circuit SD2, and the display region231 except for the region 233 is displayed by the image data V1 suppliedto the first driver circuit SD1.

In an example of a digital circuit that can be used in this embodiment,the control data SS can be transmitted through two signal lines sel1 andsel0 (see FIG. 6A). By transmitting two values (0 and 1) of high and lowpower supply voltages through each signal line, four states (fourcombinations) can be made. Three of the four states are used as thefirst-status control data SS1, the second-status control data SS2, andthe third-status control data SS3. By these control data SS, signals ofthe image data V1 or the background data V00 can be supplied to thefirst driver circuit SD1 or the second driver circuit SD2 (see FIG. 6B).

<Driver Circuit SD1, Driver Circuit SD2>

The driver circuit SD1 has a function of supplying an image signal onthe basis of the data V11. The driver circuit SD2 has a function ofsupplying an image signal on the basis of the data V12. Note that,instead of the driver circuits SD1 and SD2, a driver circuit SD in whichthe driver circuits SD1 and SD2 are integrated can be used.

For example, any of a variety of sequential circuits, such as a shiftregister, can be used as the driver circuit SD1 or SD2.

Specifically, an integrated circuit formed on a silicon substrate can beused as the driver circuit SD.

The driver circuit SD1 has a function of generating a signal to besupplied to a pixel circuit electrically connected to the reflectivedisplay element, for example. Specifically, the driver circuit SD1 has afunction of generating a signal whose polarity is inverted. Thus, forexample, the reflective liquid crystal display element can be driven.

The driver circuit SD2 has a function of generating a signal to besupplied to a pixel circuit electrically connected to the light-emittingelement, for example.

<Pixel 232(i, j)>

For example, the reflective display element and the light-emittingelement can be used in the pixel 232(i, j) (see FIG. 4C).

Specifically, the pixel 232(i, j) includes a first display element 235Aand a second display element 235B. The pixel 232(i, j) further includesa pixel circuit for driving the first display element 235A and thesecond display element 235B.

<First Display Element 235A>

For example, a display element having a function of controlling lightreflection or transmission can be used as the first display element235A. By using a reflective display element, the power consumption of adisplay panel can be reduced.

For example, a combined structure of a liquid crystal element and apolarizing plate or a MEMS shutter display element can be used.Specifically, a reflective liquid crystal display element can be used asthe first display element 235A.

The first display element 235A includes a first electrode, a secondelectrode, and a liquid crystal layer. The liquid crystal layer containsa liquid crystal material whose orientation can be controlled by avoltage applied between the first electrode and the second electrode.For example, the orientation of the liquid crystal material can becontrolled by an electric field in the thickness direction (alsoreferred to as the vertical direction), the horizontal direction, or thediagonal direction of the liquid crystal layer.

<Second Display Element 235B>

For example, a display element having a function of emitting light canbe used as the second display element 235B. Specifically, an organic ELelement can be used.

For example, an organic EL element having a function of emitting whitelight can be used as the second display element 235B. Alternatively, anorganic EL element that emits blue light, green light, or red light canbe used as the second display element 235B.

<Pixel Circuit>

A circuit having a function of driving the first display element 235A orthe second display element 235B can be used as the pixel circuit.

A switch, a transistor, a diode, a resistor, an inductor, a capacitor,or the like can be used in the pixel circuit.

For example, one or a plurality of transistors can be used as a switch.Alternatively, a plurality of transistors connected in parallel, inseries, or in combination of parallel connection and series connectioncan be used as a switch.

<Transistor>

For example, a semiconductor film formed at the same step can be usedfor transistors in the driver circuit and the pixel circuit.

For example, bottom-gate transistors, top-gate transistors, or the likecan be used.

For example, a manufacturing line for a bottom-gate transistor includingamorphous silicon as a semiconductor can be easily remodeled into amanufacturing line for a bottom-gate transistor including an oxidesemiconductor as a semiconductor. Furthermore, for example, amanufacturing line for a top-gate transistor including polysilicon as asemiconductor can be easily remodeled into a manufacturing line for atop-gate transistor including an oxide semiconductor as a semiconductor.

For example, a transistor including a semiconductor containing anelement of Group 14 can be used. Specifically, a semiconductorcontaining silicon can be used for a semiconductor film. For example,single crystal silicon, polysilicon, microcrystalline silicon, amorphoussilicon, or the like can be used for the semiconductor film of thetransistor.

Note that the temperature for forming a transistor using polysilicon asa semiconductor is lower than the temperature for forming a transistorusing single crystal silicon as a semiconductor. When low-temperaturepolysilicon (LTPS) is used, the upper limit of the process temperatureis approximately 500° C. to 550° C.

In addition, the transistor using polysilicon as a semiconductor has ahigher field-effect mobility than the transistor using amorphous siliconas a semiconductor, and therefore enables a higher aperture ratio ofpixel. Moreover, pixels arranged at an extremely high density, a gatedriver circuit, and a source driver circuit can be formed over the samesubstrate. As a result, the number of components included in anelectronic device can be reduced.

In addition, the transistor using polysilicon as a semiconductor hashigher reliability than the transistor using amorphous silicon as asemiconductor.

For example, a transistor including an oxide semiconductor can be used.Specifically, an oxide semiconductor containing indium or an oxidesemiconductor containing indium, gallium, and zinc can be used for asemiconductor film.

For example, a transistor having a lower leakage current in an off statethan a transistor that uses amorphous silicon for a semiconductor filmcan be used. Specifically, a transistor that uses an oxide semiconductorfor a semiconductor film can be used.

Accordingly, the pixel circuit can hold an image signal for a longertime than a pixel circuit including a transistor that uses amorphoussilicon for a semiconductor film. Specifically, the selection signal canbe supplied with a frequency of lower than 30 Hz, preferably lower than1 Hz, and further preferably less than once per minute while flickeringis suppressed. Consequently, eyestrain on a user of the informationprocessing device can be reduced, and power consumption for driving canbe reduced.

Alternatively, for example, a transistor including a compoundsemiconductor can be used. Specifically, a semiconductor containinggallium arsenide can be used for a semiconductor film.

For example, a transistor including an organic semiconductor can beused. Specifically, an organic semiconductor containing any ofpolyacenes and graphene can be used for the semiconductor film.

<Input Portion 240>

The input portion 240 includes an input panel.

For example, the input panel includes a proximity sensor which has afunction of sensing an approaching pointer. Note that a finger, a styluspen, or the like can be used as the pointer.

As the stylus pen, a light-emitting element such as a light-emittingdiode, a piece of metal, a coil, or the like can be used.

For example, a capacitive proximity sensor, an electromagnetic inductiveproximity sensor, an infrared light detection type proximity sensor, aproximity sensor including a photoelectric conversion element, or thelike can be used as the proximity sensor.

The capacitive proximity sensor includes a conductive film and has afunction of detecting the proximity of an object with inductivity largerthan that of the air to the conductive film. For example, a plurality ofconductive films is provided in different regions of the input panel,and a region a finger or the like serving as a pointer approaches isidentified in accordance with a change in the parasitic capacitance ofthe conductive film to determine input position coordinate data.

In addition, the electromagnetic inductive proximity sensor has afunction of detecting the proximity of a piece of metal, a coil, or thelike to the detection circuit. For example, a plurality of oscillatorcircuits is provided in different regions of the input panel, and aregion a piece of metal, a coil, or the like in a stylus pen or the likeserving as a pointer approaches can be identified in accordance with achange in the circuit constant of the oscillation circuit to determineinput position coordinate data.

For example, the photo-detection proximity sensor has a function ofdetecting the proximity of a light-emitting element. For example, aplurality of photoelectric conversion elements is provided in differentregions of the input panel, and a region a light-emitting element in astylus pen or the like serving as a pointer approaches can be identifiedin accordance with a change in the electromotive force of thephotoelectric conversion element to determine input position coordinatedata.

<Sensor Portion 250>

As the sensor portion 250, a sensor having a function of sensing thesurrounding state and supplying the sensing data P2 can be used.

For example, an illuminance sensor that senses the brightness of anenvironment, a human motion sensor, or the like can be used for thesensor portion 250.

For example, a camera, an acceleration sensor, a direction sensor, apressure sensor, a temperature sensor, a humidity sensor, an illuminancesensor, or a global positioning system (GPS) signal receiving circuitcan be used as the sensor portion 250.

<Communication Portion 290>

The communication portion 290 has a function of supplying or acquiringdata to/from a network.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 2

In this embodiment, a program that can be used for an informationprocessing device of one embodiment of the present invention isdescribed with reference to FIG. 7.

In this embodiment, a method for supplying the first-status control dataSS, the second-status control data SS, or the third-status control dataSS on the basis of the frequency of selection of the icon by theinput/output device with the use of the structure described inEmbodiment 1 is described. Furthermore, a method for supplying thefirst-status control data SS, the second-status control data SS, or thethird-status control data SS on the basis of sensing data supplied fromthe sensor portion 250 to the arithmetic device is described.

With this program, an icon with low selection frequency is displayed ata low luminance using a reflective display element, while an icon withhigh selection frequency is displayed at a high luminance using alight-emitting element and a reflective display element so as to beemphasized and displayed at high visibility.

FIG. 7 is a flow chart showing the program of one embodiment of thepresent invention.

<Program Example>

The program of one embodiment of the present invention can have astructure of improving the visibility in the following manner on thebasis of the illuminance of the environment where the informationprocessing device 200 is placed and the frequency of selection of theicon by the input/output device, in addition to the structure of theprogram described in Embodiment 1.

The icon with high selection frequency is displayed using thelight-emitting element and the reflective display element.

In the case where the information processing device 200 is used in a dimor dark environment, the icon with low selection frequency is displayedusing the light-emitting element. Thus, the image data can be favorablydisplayed even in a dark environment.

In the case where the information processing device 200 is used in abright environment, the icon with low selection frequency is displayedusing the reflective display element.

As in Embodiment 1, the reflective display element is used when thefirst-status control data is supplied. Furthermore, the light-emittingelement is used when the second-status control data is supplied.Moreover, both the reflective display element and the light-emittingelement are used when the third-status control data is supplied.

That is, the program includes the following steps.

<First to Third Steps>

In the first to third steps ((T1) to (T3) in FIG. 7), in the same way asthe steps (T1) to (T3) in FIG. 2, whether there is an input from theinput portion 240 is determined, the input position coordinate data P1supplied from the input portion 240 is read, and whether there is anoverlap with the displayed icon is determined.

In the case where there is not an overlap with the displayed icon, thefifth step ((T5) in FIG. 7) is selected. In the case where there is anoverlap with the displayed icon, the next fourth step ((T4) in FIG. 7)is selected.

<Fourth Step>

In the fourth step, the selection frequency of the icon that has anoverlap according to the determination in the third step ((T3) in FIG.7), that is, the selected icon is determined by the arithmetic device210.

When it is determined that the icon is frequently selected, the next(7-3)th step ((T7-3) in FIG. 7) is selected, and the third-statuscontrol data SS is supplied in accordance with the data of thecoordinates at which the icon is displayed, that is, icon coordinatedata. The selection frequency is determined by whether the number oftimes the icon is selected so far from the time of input is more than orequal to a predetermined threshold value. In addition, the selectionnumber of times is updated every input. Here, the selection circuit 239supplies the image data V1 to the first driver circuit SD1 and thesecond driver circuit SD2 on the basis of the third-status control dataSS (see FIG. 1B).

Furthermore, when it is determined that the icon is not selectedfrequently, the fifth step ((T5) in FIG. 7) is selected.

<Fifth Step>

In the fifth step, an illuminance sensor is used for the sensor portion250 and the sensing data P2 about the illuminance is supplied to thesensor portion 250 to compare the sensing data P2 with a predeterminedvalue.

<Sixth Step>

In the sixth step, which the first-status control data or thesecond-status control data is supplied is determined on the basis of thesensing data P2 about the outside environment, that is, illuminance.When the environment where the information processing device 200 is usedis bright, the first-status control data is supplied and the reflectivedisplay element performs display ((T7-1) in FIG. 7). When theenvironment is dim or dark, the second-status control data is suppliedand the light-emitting element performs display ((T7-2) in FIG. 7).

When the environment where the information processing device 200 is usedis bright, the selection circuit 239 supplies the image data V1 and thebackground data to the first driver circuit SD1 and the second drivercircuit SD2, respectively, on the basis of the first-status control dataSS (see FIG. 1B). When the environment is dim or dark, the selectioncircuit 239 supplies the image data V1 and the background data to thesecond driver circuit SD2 and the first driver circuit SD1,respectively, on the basis of the second-status control data SS (seeFIG. 1B).

Thus, the status of the control data can be determined on the basis ofthe sensing data such as illuminance and the selection frequency of theicon. As a result, the reflective display element, the light-emittingelement, or both of them is selected, and the image data can bedisplayed using the selected reflective display element and/or theselected light-emitting element.

Note that this embodiment can be appropriately combined with any of theother embodiments in this specification as appropriate.

Embodiment 3

In this embodiment, a program that can be used for an informationprocessing device of one embodiment of the present invention isdescribed with reference to FIG. 8.

In this embodiment, the displaying method of a region selected by theinput/output device can be changed. In the information processing deviceof this embodiment, when normal display is performed using thelight-emitting element and a defect arises owing to a malfunction in adriver circuit for the light-emitting element, coordinate data of thedefect region may be input from the input/output device with a touchsensor or the like, so that display can be performed by the reflectivedisplay element in addition to the light-emitting element.

By the program of this embodiment, the region selected by theinput/output device is displayed by the reflective display element andthe light-emitting element, and the region that is not selected isdisplayed by the light-emitting element only.

This embodiment can be similarly used in the case where normal displayis performed using the reflective display element and display isperformed by the light-emitting element in addition to the reflectivedisplay element.

FIG. 8 is a flow chart showing the program of one embodiment of thepresent invention.

<Program Example>

<First Step>

In the first step ((U1) in FIG. 8), whether there is an input from theinput portion 240 is determined. If there is an input, the second stepis selected.

<Second Step>

In the second step ((U2) in FIG. 8), the input position coordinate dataP1 supplied from the input portion 240 is read. In this embodiment, apointer that spreads with a certain radius from the center of thecoordinates of the input position coordinate data P1 is displayed. Inthis specification, the region where the pointer is displayed isreferred to as a pointer display region. Then, the third step isselected.

<Third Step>

In the third step, the third-status control data SS is supplied towardcoordinates of the pointer display region set in the second step in thedisplay portion ((U3) in FIG. 8). Then, display is performed by thereflective display element and the light-emitting element in theposition to which the third-status control data is input. Thus, thedefect region can be complementarily displayed, improving visibility.

<Fourth Step>

In the fourth step, whether a certain period of time has passed from thelast input from the input portion is determined. In the certain periodof time, the displayed image can be recognized. After the certain periodof time, the fifth step for returning to normal display is selected.

<Fifth Step>

In the fifth step, control data for normal display, that is, thefirst-status control data or the second-status control data, is suppliedtoward coordinates corresponding to the pointer display region in thedisplay portion. The displaying method for normal display is the methodfor displaying the icon with low selection frequency on the basis of thesensing data P2 as described in Embodiment 2. By returning to normaldisplay in this manner, the emphasized portion can be updated.

When there are a plurality of input position coordinate data P1, thepointer display region may be a total region for the plurality of inputposition coordinate data P1.

Note that the input in this embodiment may be the input of sensing data,the input of the input position coordinate data, or the input of both ofthem. This embodiment can be combined with any of the other embodimentsdescribed in this specification as appropriate.

Embodiment 4

In this embodiment, the structure of a display panel of one embodimentof the present invention will be described with reference to FIGS. 9A,9B1, and 9B2, FIG. 10, FIGS. 11A, 11B1, and 11B2, FIGS. 19A to 19C, andFIGS. 20A and 20B.

FIGS. 9A, 9B1, and 9B2 illustrate the structure of a display panel 700of one embodiment of the present invention. FIG. 9A is a bottom view ofthe display panel 700 of one embodiment of the present invention. FIG.9B1 is a bottom view illustrating part of FIG. 9A. FIG. 9B2 is a bottomview omitting some components illustrated in FIG. 9B1.

FIGS. 19A to 19C illustrate the structure of the display panel 700 ofone embodiment of the present invention. FIG. 19A is a cross-sectionalview taken along lines X1-X2, X3-X4, X5-X6, X7-X8, X9-X10, and X11-X12in FIG. 9A. FIG. 19B is a cross-sectional view illustrating thestructure of part of the display panel and FIG. 19C is a cross-sectionalview illustrating the structure of another part of the display panel.

FIG. 10 illustrates the structure of the display panel 700 of oneembodiment of the present invention. FIG. 10 is a circuit diagram of apixel circuit 530(i, j) and a pixel circuit 530(i, j+1) which areincluded in the display panel 700 of one embodiment of the presentinvention.

FIGS. 11A, 11B1, and 11B2 illustrate the structure of a display panel700 of one embodiment of the present invention. FIG. 11A is a blockdiagram illustrating arrangement of pixels, wirings, or the like whichcan be used for the display panel 700 of one embodiment of the presentinvention. FIGS. 11B1 and 11B2 are schematic views illustrating thearrangement of openings 751H which can be used for the display panel 700of one embodiment of the present invention.

<Structure Example 1 of Display Panel>

The display panel 700 described in this embodiment includes a signalline 1(j) and a pixel 702(i, j) (see FIGS. 9B1 and 9B2).

The pixel 702(i, j) is electrically connected to the signal line S1(j).

The pixel 702(i, j) includes a first display element 750(i, j), a firstconductive film, a second conductive film, an insulating film 501C, thepixel circuit 530(i, j), and a second display element 550(i, j) (seeFIG. 19A and FIG. 10).

The first conductive film is electrically connected to the first displayelement 750(i, j) (see FIG. 19A). For example, the first conductive filmcan be used for the first electrode 751(i, j) of the first displayelement 750(i, j).

The second conductive film has a region overlapping with the firstconductive film. For example, the second conductive film can be used asa conductive film 512B serving as a source electrode or a drainelectrode of a transistor which can be used as a switch SW1.

The insulating film 501C has a region interposed between the secondconductive film and the first conductive film.

The pixel circuit 530(i, j) is electrically connected to the secondconductive film. For example, the transistor in which the secondconductive film is used as the conductive film 512B serving as a sourceelectrode or a drain electrode can be used as the switch SW1 of thepixel circuit 530(i, j) (see FIG. 19A and FIG. 10).

The second display element 550(i, j) is electrically connected to thepixel circuit 530(i, j).

The insulating film 501C includes an opening 591A (see FIG. 19A).

The second conductive film is electrically connected to the firstconductive film in the opening 591A. For example, the conductive film512B is electrically connected to the first electrode 751(i, j) whichalso serves as the first conductive film.

The pixel circuit 530(i, j) is electrically connected to the signal lineS1(j) (see FIG. 10). Note that the conductive film 512A is electricallyconnected to the signal line S1(j) (see FIG. 10 and FIG. 19A).

The first electrode 751(i, j) has an edge portion embedded in theinsulating film 501C.

Furthermore, the pixel circuit 530(i, j) of the display panel describedin this embodiment includes the switch SW1. The switch SW1 includes atransistor that includes an oxide semiconductor.

The second display element 550(i, j) of the display panel described inthis embodiment has a viewing angle overlapping with part of a viewingangle of the first display element 750(i, j). In other words, the seconddisplay element 550(i, j) has a function of performing display in thesame direction as any of display directions of the first display element750(i, j). For example, a dashed arrow in the drawing denotes thedirection in which the first display element 750(i, j) performs displayby adjusting the intensity of external light reflection. In addition, asolid arrow in the drawing denotes the direction in which the seconddisplay element 550(i, j) performs display (see FIG. 19A).

In addition, the second display element 550(i, j) of the display paneldescribed in this embodiment has a function of displaying in a regionsurrounded by a region where the first display element 750(i, j)performs display (see FIG. 11B1 or 11B2). Note that the first displayelement 750(i, j) performs display in a region overlapping with thefirst electrode 751(i, j) and that the second display element 550(i, j)performs display in a region overlapping with the opening 751H.

Furthermore, the first display element 750(i, j) of the display paneldescribed in this embodiment includes a reflective film which reflectsincident light and has a function of adjusting the intensity of thereflected light. The reflective film has the opening 751H. Note that forexample, the first conductive film, the first electrode 751(i, j), orthe like can be used as the reflective film of the first display element750(i, j).

Furthermore, the second display element 550(i, j) has a function ofemitting light toward the opening 751H.

In addition, the display panel described in this embodiment includes thepixel 702(i, j), one pixel group consisting of pixels 702(i, 1) to702(i, n), another pixel group consisting of pixels 702(1, j) to 702(m,j), and a scan line G1(i) (see FIG. 11A). Note that i is an integergreater than or equal to 1 and less than or equal to m, j is an integergreater than or equal to 1 and less than or equal to n, and each of mand n is an integer greater than or equal to 1.

The display panel described in this embodiment includes a scan lineG2(i), a wiring CSCOM, and a wiring ANO.

The one pixel group consisting of the pixels 702(i, 1) to 702(i, n)includes the pixel 702(i, j), and are arranged in a row direction(indicated by an arrow R in the drawing).

The other pixel group consisting of the pixels 702(1, j) to 702(m, j)includes the pixel 702(i, j), and are arranged in a column direction(indicated by an arrow C in the drawing) intersecting with the rowdirection.

The scan line G1(i) is electrically connected to group of the pixels702(i, 1) to 702(i, n) arranged in the row direction.

The signal line S1(j) is electrically connected to the other group ofthe pixels 702(1, j) to 702(m, j) arranged in the column direction.

For example, the pixel 702(i, j+1) adjacent to the pixel 702(i, j) inthe row direction includes an opening in a position different from thatof the opening 751H in the pixel 702(i, j) (see FIG. 11B1).

For example, the pixel 702(i+1, j) adjacent to the pixel 702(i, j) inthe column direction includes an opening in a position different fromthat of the opening 751H in the pixel 702(i, j) (see FIG. 11B2). Notethat for example, the first electrode 751(i, j) can be used as thereflective film.

The display panel described in this embodiment includes a first displayelement, a first conductive film electrically connected to the firstdisplay element, a second conductive film having a region overlappingwith the first conductive film, an insulating film having a regionsandwiched between the second conductive film and the first conductivefilm, a pixel circuit electrically connected to the second conductivefilm, and a second display element electrically connected to the pixelcircuit. The insulating film has an opening. The second conductive filmis electrically connected to the first conductive film in the opening.

Accordingly, the first display element and the second display elementwhich perform display using different methods can be driven, forexample, with the pixel circuit which can be formed in the same process.As a result, a novel display panel that is highly convenient can beprovided.

In addition, the display panel described in this embodiment includes aterminal 519B and a conductive film 511B (see FIG. 19A).

The insulating film 501C has a region interposed between the terminal519B and the conductive film 511B. In addition, the insulating film 501Cincludes an opening 591B.

The terminal 519B is electrically connected to the conductive film 511Bin the opening 591B. In addition, the conductive film 511B iselectrically connected to the pixel circuit 530(i, j). Note that forexample, when the first electrode 751(i, j) or the first conductive filmis used as the reflective film, a surface serving as a contact with theterminal 519B is oriented in the same direction as a surface of thefirst electrode 751(i, j) that faces light incident to the first displayelement 750(i, j).

Thus, power or signals can be supplied to the pixel circuit through theterminal. As a result, a novel display panel that is highly convenientcan be provided.

In addition, the first display element 750(i, j) of the display paneldescribed in this embodiment includes a layer 753 containing aliquid-crystal material, the first electrode 751(i, j), and a secondelectrode 752. Note that the second electrode 752 is provided so that anelectric field for controlling the alignment of the liquid crystalmaterial is generated between the second electrode 752 and the firstelectrode 751(i, j).

Furthermore, the display panel described in this embodiment includes analignment film AF1 and an alignment film AF2. The alignment film AF2 isprovided so that the layer 753 containing a liquid crystal material isinterposed between the alignment films AF1 and AF2.

In addition, the second display element 550(i, j) of the display paneldescribed in this embodiment includes a third electrode 551(i, j), afourth electrode 552, and a layer 553(j) containing a light-emittingorganic compound.

The fourth electrode 552 has a region overlapping with the thirdelectrode 551(i, j). The layer 553(j) containing a light-emittingorganic compound is positioned between the third electrode 551(i, j) andthe fourth electrode 552. The third electrode 551(i, j) is electricallyconnected to the pixel circuit 530(i, j) in a contact portion 522.

Moreover, the pixel 702(i, j) of the display panel described in thisembodiment includes a coloring film CF1, a light-blocking film BM, aninsulating film 771, and a functional film 770P.

The coloring film CF1 has a region overlapping with the first displayelement 750(i, j). The light-blocking film BM has an opening in a regionoverlapping with the first display element 750(i, j).

The insulating film 771 is positioned between the coloring film CF1 andthe layer 753 containing a liquid crystal material or between thelight-blocking film BM and the layer 753 containing a liquid crystalmaterial. Thus, unevenness due to the thickness of the coloring film CF1can be avoided. Alternatively, impurities can be prevented from beingdiffused from the light-blocking film BM, the coloring film CF1, or thelike to the layer 753 containing a liquid crystal material.

The functional film 770P has a region overlapping with the first displayelement 750(i, j). The functional film 770P is provided so that asubstrate 770 is interposed between the functional film 770P and thefirst display element 750(i, j).

In addition, the display panel described in this embodiment includes asubstrate 570, the substrate 770, and a functional layer 520.

The substrate 770 has a region overlapping with the substrate 570. Thefunctional layer 520 is positioned between the substrates 570 and 770.

The functional layer 520 includes the pixel circuit 530(i, j), thesecond display element 550(i, j), an insulating film 521, and aninsulating film 528. Furthermore, the functional layer 520 includes aninsulating film 518 and an insulating film 516.

The insulating film 521 is positioned between the pixel circuit 530(i,j) and the second display element 550(i, j).

The insulating film 528 is positioned between the insulating film 521and the substrate 570 and has an opening in a region overlapping withthe second display element 550(i, j). The insulating film 528 along theedge of the third electrode 551 can avoid a short circuit between thethird electrode 551 and the fourth electrode 552.

The insulating film 518 has a region positioned between the insulatingfilm 521 and the pixel circuit 530(i, j). The insulating film 516 has aregion positioned between the insulating film 518 and the pixel circuit530(i, j).

Moreover, the display panel described in this embodiment includes abonding layer 505, a sealant 705, and a structure body KB1.

The bonding layer 505 is positioned between the functional layer 520 andthe substrate 570 and has a function of bonding the functional layer 520and the substrate 570.

The sealant 705 is positioned between the functional layer 520 and thesubstrate 770 and has a function of bonding the functional layer 520 andthe substrate 770.

The structure body KB1 has a function of making a predetermined gapbetween the functional layer 520 and the substrate 770.

In addition, the display panel described in this embodiment includes aterminal 519C, a conductive film 511C, and a conductor CP.

The insulating film 501C has a region interposed between the terminal519C and the conductive film 511C. In addition, the insulating film 501Chas an opening 591C.

The terminal 519C is electrically connected to the conductive film 511Cin the opening 591C. In addition, the conductive film 511C iselectrically connected to the pixel circuit 530(i, j).

The conductor CP is interposed between the terminal 519C and the secondelectrode 752 for electrically connecting the terminal 519C and thesecond electrode 752. For example, a conductive particle can be used asthe conductor CP.

Moreover, the display panel described in this embodiment includes adriver circuit GD and a driver circuit SD (see FIGS. 9A and 11A).

The driver circuit GD is electrically connected to the scan line G1(i).The driver circuit GD includes, for example, a transistor MD.Specifically, a transistor which includes a semiconductor film and canbe formed in the same step as the transistor included in the pixelcircuit 530(i, j) can be used as the transistor MD (see FIGS. 19A and19C).

The driver circuit SD is electrically connected to the signal lineS1(j). The driver circuit SD is electrically connected to a terminalusing a conductive material, for example. The terminal can be formed inthe same step as the terminal 519B or the terminal 519C.

Individual components of the display panel will be described below. Notethat these components cannot be clearly distinguished and one componentserves as another one or includes part of another one in some cases.

For example, the first conductive film can be used as the firstelectrode 751(i, j). The first conductive film can be used as areflective film.

In addition, the second conductive film can be used as the conductivefilm 512B serving as a source electrode or a drain electrode of atransistor.

<<Structure Example 1>>

The display panel of one embodiment of the present invention includesthe substrate 570, the substrate 770, the structure body KB1, thesealant 705, or the bonding layer 505.

In addition, the display panel of one embodiment of the presentinvention includes the functional layer 520, the insulating film 521,and the insulating film 528.

In addition, the display panel of one embodiment of the presentinvention includes the signal line S1(j), the signal line S2(j), thescan line G1(i), the scan line G2(i), the wiring CSCOM, and the wiringANO.

In addition, the display panel of one embodiment of the presentinvention includes the first conductive film or the second conductivefilm.

In addition, the display panel of one embodiment of the presentinvention includes the terminal 519B, the terminal 519C, the conductivefilm 511B, or the conductive film 511C.

In addition, the display panel of one embodiment of the presentinvention includes the pixel circuit 530(i, j) or the switch SW1.

In addition, the display panel of one embodiment of the presentinvention includes the first display element 750(i, j), the firstelectrode 751(i, j), the reflective film, the opening 751H, the layer753 containing a liquid crystal material, and the second electrode 752.

In addition, the display panel of one embodiment of the presentinvention includes the alignment film AF1, the alignment film AF2, thecoloring film CF1, the light-blocking film BM, the insulating film 771,and the functional film 770P.

In addition, the display panel of one embodiment of the presentinvention includes the second display element 550(i, j), the thirdelectrode 551(i, j), the fourth electrode 552, or the layer 553(j)containing a light-emitting organic compound.

Furthermore, the display panel of one embodiment of the presentinvention includes the insulating film 501C.

In addition, the display panel of one embodiment of the presentinvention includes the driver circuit GD or the driver circuit SD.

<<Substrate 570>>

The substrate 570 and the like can be formed using a material havingheat resistance high enough to withstand heat treatment in themanufacturing process. Specifically, a non-alkali glass which ispolished to a thickness of approximately 0.7 mm or 0.1 mm can be used

For example, a large-sized glass substrate having any of the followingsizes can be used as the substrate 570 and the like: the 6th generation(1500 mm×1850 mm), the 7th generation (1870 mm×2200 mm), the 8thgeneration (2200 mm×2400 mm), the 9th generation (2400 mm×2800 mm), andthe 10th generation (2950 mm×3400 mm). Thus, a large-sized displaydevice can be manufactured.

For the substrate 570 and the like, an organic material, an inorganicmaterial, a composite material of an organic material and an inorganicmaterial, or the like can be used. For example, an inorganic materialsuch as glass, ceramic, or a metal can be used for the substrate 570 andthe like.

Specifically, non-alkali glass, soda-lime glass, potash glass, crystalglass, quartz, sapphire, or the like can be used for the substrate 570and the like. Specifically, an inorganic oxide film, an inorganicnitride film, an inorganic oxynitride film, or the like can be used forthe substrate 570 and the like. For example, a film of silicon oxide,silicon nitride, silicon oxynitride, aluminum oxide, or the like can beused for the substrate 570 and the like. Stainless steel, aluminum, orthe like can be used for the substrate 570 and the like.

For example, a single crystal semiconductor substrate or apolycrystalline semiconductor substrate of silicon or silicon carbide, acompound semiconductor substrate of silicon germanium, or an SOIsubstrate can be used as the substrate 570 and the like. Thus, asemiconductor element can be formed over the substrate 570 and the like.

For example, an organic material such as a resin, a resin film, orplastic can be used for the substrate 570 and the like. Specifically, aresin film or resin plate of polyester, polyolefin, polyamide,polyimide, polycarbonate, an acrylic resin, or the like can be used forthe substrate 570 and the like.

For example, a composite material, such as a resin film to which a metalplate, a thin glass plate, or an inorganic film is bonded can be usedfor the substrate 570 and the like. For example, a composite materialformed by dispersing a fibrous or particulate metal, glass, inorganicmaterial, or the like into a resin film can be used for the substrate570 and the like. For example, a composite material formed by dispersinga fibrous or particulate resin, organic material, or the like into aninorganic material can be used for the substrate 570 and the like.

A single-layer material or a material in which a plurality of layers arestacked can be used for the substrate 570 and the like. For example, amaterial in which a base, an insulating film that prevents diffusion ofimpurities contained in the base, and the like are stacked can be usedfor the substrate 570 and the like. Specifically, a material in whichglass and one or a plurality of films that prevent diffusion ofimpurities contained in the glass and that are selected from a siliconoxide layer, a silicon nitride layer, a silicon oxynitride layer, andthe like are stacked can be used for the substrate 570 and the like.Alternatively, a material in which a resin and a film for preventingdiffusion of impurities that penetrate the resin, such as a siliconoxide film, a silicon nitride film, and a silicon oxynitride film arestacked can be used for the substrate 570 and the like.

Specifically, a resin film, a resin plate, a stack, or the like ofpolyester, polyolefin, polyamide, polyimide, polycarbonate, an acrylicresin, or the like can be used for the substrate 570 and the like.

Specifically, a material including polyester, polyolefin, polyamide(e.g., nylon or aramid), polyimide, polycarbonate, polyurethane, anacrylic resin, an epoxy resin, or a resin having a siloxane bond, suchas silicone, can be used for the substrate 570 and the like.

Specifically, polyethylene terephthalate (PET), polyethylene naphthalate(PEN), polyethersulfone (PES), acrylic, or the like can be used for thesubstrate 570 and the like.

Alternatively, paper, wood, or the like can be used for the substrate570 and the like.

For example, a flexible substrate can be used as the substrate 570 andthe like.

Note that a transistor, a capacitor, or the like can be directly formedon the substrate. Alternatively, a transistor, a capacitor, or the likecan be formed over a substrate that is for use in manufacturingprocesses and withstands heat applied in the processes, and then can betransferred to the substrate 570 or the like. Accordingly, a transistor,a capacitor, or the like can be formed over a flexible substrate.

<<Substrate 770>>

For example, a light-transmitting material can be used for the substrate770. Specifically, a material selected from the materials used for thesubstrate 570 can be used for the substrate 770. Specifically, anon-alkali glass which is polished to a thickness of approximately 0.7mm or 0.1 mm can be used.

<<Structure Body KB1>>

For example, an organic material, an inorganic material, or a compositematerial of an organic material and an inorganic material can be usedfor the structure body KB1 or the like. Thus, components between whichthe structure body KB1 or the like is interposed can have apredetermined gap.

Specifically, for the structure body KB1 or the like, polyester,polyolefin, polyamide, polyimide, polycarbonate, polysiloxane, anacrylic resin, or the like, or a composite material of plural kinds ofresins selected from these can be used. Alternatively, a photosensitivematerial may be used.

<<Sealant 705>>

For the sealant 705 or the like, an inorganic material, an organicmaterial, a composite material of an inorganic material and an organicmaterial, or the like can be used.

For example, an organic material such as a thermally fusible resin or acurable resin can be used for the sealant 705 or the like.

For the sealant 705 or the like, an organic material such as a reactivecurable adhesive, a photo-curable adhesive, a thermosetting adhesive,and/or an anaerobic adhesive can be used.

Specifically, an adhesive containing an epoxy resin, an acrylic resin, asilicone resin, a phenol resin, a polyimide resin, an imide resin, apolyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB) resin, or anethylene vinyl acetate (EVA) resin, or the like can be used for thesealant 705 or the like.

<<Bonding Layer 505>>

For example, a material that can be used for the sealant 705 can be usedfor the bonding layer 505.

<<Insulating Film 521>>

For example, an insulating inorganic material, an insulating organicmaterial, or an insulating composite material containing an inorganicmaterial and an organic material can be used for the insulating film 521or the like.

Specifically, an inorganic oxide film, an inorganic nitride film, aninorganic oxynitride film, or a material obtained by stacking any ofthese films can be used for the insulating film 521 or the like. Forexample, a film including any of a silicon oxide film, a silicon nitridefilm, a silicon oxynitride film, and an aluminum oxide film, or a filmincluding a material obtained by stacking any of these films can be usedfor the insulating film 521 or the like.

Specifically, polyester, polyolefin, polyamide, polyimide,polycarbonate, polysiloxane, an acrylic resin, or a stacked or compositematerial including resins selected from these, or the like can be usedfor the insulating film 521 or the like. Alternatively, a photosensitivematerial may be used.

Thus, for example, steps due to components overlapping with theinsulating film 521 can be eliminated.

<<Insulating Film 528>>

For example, a material that can be used for the insulating film 521 canbe used for the insulating film 528 or the like. Specifically, a1-μm-thick film containing polyimide can be used for the insulating film528.

<<Insulating Film 501C>>

For example, the material that can be used for the insulating film 521can be used for the insulating film 501C. Specifically, a materialcontaining silicon and oxygen can be used for the insulating film 501C.Thus, impurity diffusion into the pixel circuit or the second displayelement can be suppressed.

For example, a 200-nm-thick film containing silicon, oxygen, andnitrogen can be used as the insulating film 501C.

Note that the insulating film 501C includes the opening 591A, 591B, or591C.

<<Wiring, Terminal, Conductive Film>>

A conductive material can be used for a wiring or the like.Specifically, the conductive material can be used for the signal lineS1(j), the signal line S2(j), the scan line G1(i), the scan line G2(i),the wiring CSCOM, the wiring ANO, the terminal 519B, the terminal 519C,the conductive film 511B, the conductive film 511C, or the like.

For example, an inorganic conductive material, an organic conductivematerial, a metal material, a conductive ceramic material, or the likecan be used for the wiring or the like.

Specifically, a metal element selected from aluminum, gold, platinum,silver, copper, chromium, tantalum, titanium, molybdenum, tungsten,nickel, iron, cobalt, palladium, and manganese, or the like can be usedfor the wiring or the like. Alternatively, an alloy including any of theabove-described metal elements, or the like can be used for the wiringor the like. In particular, an alloy of copper and manganese is suitablyused in microfabrication with the use of a wet etching method.

Specifically, a two-layer structure in which a titanium film is stackedover an aluminum film, a two-layer structure in which a titanium film isstacked over a titanium nitride film, a two-layer structure in which atungsten film is stacked over a titanium nitride film, a two-layerstructure in which a tungsten film is stacked over a tantalum nitridefilm or a tungsten nitride film, a three-layer structure in which atitanium film, an aluminum film, and a titanium film are stacked in thisorder, or the like can be used for the wiring or the like.

Specifically, a conductive oxide such as indium oxide, indium tin oxide,indium zinc oxide, zinc oxide, or zinc oxide to which gallium is addedcan be used for the wiring or the like.

Specifically, a film containing graphene or graphite can be used for thewiring or the like.

For example, a film including graphene oxide is formed and is reduced,so that a film including graphene can be formed. As a reducing method, amethod using heat, a method using a reducing agent, or the like can beemployed.

Specifically, a conductive high molecule can be used for the wiring orthe like.

<<First Conductive Film, Second Conductive Film>>

For example, the material that can be used for the wiring or the likecan be used for the first conductive film or the second conductive film.

The first electrode 751(i, j), the wiring, or the like can be used forthe first conductive film.

The conductive film 512B, the wiring, or the like of the transistor thatcan be used as the switch SW1 can be used as the second conductive film.

<<Pixel Circuit 530(i,j)>>

The pixel circuit 530(i, j) is electrically connected to the signal lineS1(j), the signal line S2(j), the scan line G1(i), the scan line G2(i),the wiring CSCOM, and the wiring ANO (see FIG. 10).

The pixel circuit 530(i, j+1) is electrically connected to a signal lineS1(j+1), a signal line S2(j+1), a scan line G1(i), a scan line G2(i),the wiring CSCOM, and the wiring ANO.

Note that in the case where a voltage used as a signal supplied to thesignal line S2(j) is different from a voltage used as a signal suppliedto the signal line S1(j+1), the signal line S1(j+1) is positioned apartfrom the signal line S2(j). Specifically, the signal line S2(j+1) ispositioned adjacent to the signal line S2(j).

The pixel circuit 530(i, j) includes the switch SW1, a capacitor C1, aswitch SW2, a transistor M, and a capacitor C2.

For example, a transistor including a gate electrode electricallyconnected to the scan line G1(i) and a first electrode electricallyconnected to the signal line S1(j) can be used as the switch SW1.

The capacitor C1 includes a first electrode electrically connected to asecond electrode of the transistor used as the switch SW1 and a secondelectrode electrically connected to the wiring CSCOM.

For example, a transistor that includes a gate electrode electricallyconnected to the scan line G2(i) and includes a first electrodeelectrically connected to the signal line S2(j) can be used as theswitch SW2.

The transistor M includes a gate electrode electrically connected to thesecond electrode of the transistor used as the switch SW2, and a firstelectrode electrically connected to the wiring ANO.

Note that a transistor that includes a semiconductor film providedbetween a gate electrode and a conductive film can be used as thetransistor M. For example, a conductive film electrically connected to awiring that can supply the same potential as the first electrode of thetransistor M can be used.

The capacitor C2 includes a first electrode electrically connected to asecond electrode of a transistor used as the switch SW2 and a secondelectrode electrically connected to the first electrode of thetransistor M.

Note that the first electrode of the first display element 750(i, j) iselectrically connected to the second electrode of the transistor used asthe switch SW1, and the second electrode of the first display element750(i, j) is electrically connected to the wiring VCOM1. Accordingly,the first display element 750(i, j) can be driven.

In addition, the first electrode of the second display element 550(i, j)is electrically connected to the second electrode of the transistor Mand the second electrode of the second display element 550(i, j) iselectrically connected to and the wiring VCOM2. Accordingly, the seconddisplay element 550(i, j) can be driven.

<<Switch SW1, Switch SW2, Transistor M, Transistor MD>>

For example, a bottom-gate transistor, a top-gate transistor, or thelike can be used as the switch SW1, the switch SW2, the transistor M,the transistor MD, or the like.

For example, a transistor using a semiconductor containing an element ofGroup 14 for a semiconductor film can be used. Specifically, asemiconductor containing silicon can be used for the semiconductor film.For example, single crystal silicon, polysilicon, microcrystallinesilicon, amorphous silicon, or the like can be used for thesemiconductor film of the transistor.

For example, a transistor using an oxide semiconductor for asemiconductor film can be used. Specifically, an oxide semiconductorcontaining indium or an oxide semiconductor containing indium, gallium,and zinc can be used for a semiconductor film.

For example, a transistor having a lower leakage current in an off statethan a transistor that uses amorphous silicon for a semiconductor filmcan be used as the switch SW1, the switch SW2, the transistor M, thetransistor MD, or the like. Specifically, a transistor using an oxidesemiconductor for a semiconductor film 508 can be used as the switchSW1, the switch SW2, the transistor M, the transistor MD, or the like.

Thus, a pixel circuit can hold an image signal for a longer time than apixel circuit including a transistor that uses amorphous silicon for asemiconductor film. Specifically, the selection signal can be suppliedwith a frequency of lower than 30 Hz, preferably lower than 1 Hz, andmore preferably less than once per minute while flickering issuppressed. Consequently, eyestrain on a user of the informationprocessing device can be reduced, and power consumption for driving canbe reduced.

The transistor that can be used as the switch SW1 includes thesemiconductor film 508 and the conductive film 504 having a regionoverlapping with the semiconductor film 508 (see FIG. 19B). Furthermore,the transistor that can be used as the switch SW1 includes theconductive film 512A and the conductive film 512B.

Note that the conductive film 504 and the insulating film 506 serve as agate electrode and a gate insulating film, respectively. Furthermore,the conductive film 512A has one of a function as a source electrode anda function as a drain electrode, and the conductive film 512B has theother.

In addition, a transistor that includes the semiconductor film 508provided between the conductive film 504 and the conductive film 524 canbe used as the transistor M (see FIG. 19C).

A conductive film in which a 10-nm-thick film containing tantalum andnitrogen and a 300-nm-thick film containing copper are stacked in thisorder can be used as the conductive film 504.

A material in which a 400-nm-thick film containing silicon and nitrogenand a 200-nm-thick film containing silicon, oxygen, and nitrogen arestacked can be used for the insulating film 506.

A 25-nm-thick film containing indium, gallium, and zinc can be used asthe semiconductor film 508.

A conductive film in which a 50-nm-thick film containing tungsten, a400-nm-thick film containing aluminum, and a 100-nm-thick filmcontaining titanium are stacked in this order can be used as theconductive film 512A or 512B.

<<First Display Element 750(i, j)>>

For example, a display element having a function of controllingtransmission or reflection of light can be used as the first displayelement 750(i, j) or the like. For example, a combined structure of aliquid crystal element and a polarizing plate or a MEMS shutter displayelement can be used. Specifically, the use of a reflective displayelement can reduce the power consumption of a display panel. Forexample, a reflective liquid crystal display element can be used as thefirst display element 750.

Specifically, a liquid crystal element driven in any of the followingdriving modes can be used: an in-plane-switching (IPS) mode, a twistednematic (TN) mode, a fringe field switching (FFS) mode, an axiallysymmetric aligned micro-cell (ASM) mode, an optically compensatedbirefringence (OCB) mode, a ferroelectric liquid crystal (FLC) mode, anantiferroelectric liquid crystal (AFLC) mode, and the like.

In addition, a liquid crystal element that can be driven by, forexample, a vertical alignment (VA) mode such as a multi-domain verticalalignment (MVA) mode, a patterned vertical alignment (PVA) mode, anelectrically controlled birefringence (ECB) mode, a continuous pinwheelalignment (CPA) mode, or an advanced super view (ASV) mode can be used.

For example, thermotropic liquid crystal, low-molecular liquid crystal,high-molecular liquid crystal, polymer dispersed liquid crystal,ferroelectric liquid crystal, anti-ferroelectric liquid crystal, or thelike can be used. A liquid crystal material that exhibits a cholestericphase, a smectic phase, a cubic phase, a chiral nematic phase, anisotropic phase, or the like can be used. Alternatively, a liquidcrystal material that exhibits a blue phase can be used.

<<First Electrode 751(i, j)>>

For example, the material of the wiring or the like can be used for thefirst electrode 751(i, j). Specifically, a reflective film can be usedfor the first electrode 751(i, j).

<<Reflective Film>>

For example, a material reflecting visible light can be used for thereflective film. Specifically, a material containing silver can be usedfor the reflective film. For example, a material containing silver,palladium, and the like or a material containing silver, copper, and thelike can be used for the reflective film.

The reflective film reflects, for example, light passing through thelayer 753 containing a liquid crystal material. This allows the firstdisplay element 750 to serve as a reflective liquid crystal element.Alternatively, a material with an uneven surface can be used for thereflective film. In that case, incident light can be reflected invarious directions so that a white image can be displayed.

Note that one embodiment of the present invention is not limited to thestructure in which the first electrode 751(i, j) is used as thereflective film. For example, a structure in which the reflective filmis positioned between the layer 753 containing a liquid crystal materialand the first electrode 751(i, j) can be used. Alternatively, astructure in which the first electrode 751(i, j) havinglight-transmitting properties is positioned between the reflective filmand the layer 753 containing a liquid crystal material can be used.

<<Opening 751H>>

If the ratio of the total area of the opening 751H to the total areaexcept for the opening is too high, display performed using the firstdisplay element 750(i, j) is dark. If the ratio of the total area of theopening 751H to the total area except for the opening is too low,display performed using the second display element 550(i, j) is dark.

Also, if the area of the opening 751H in the reflective film is toosmall, light emitted from the second display element 550 is notefficiently extracted.

The opening 751H may have a polygonal shape, a quadrangular shape, anelliptical shape, a circular shape, a cross-like shape, or the like. Theopening 751H may also have a stripe shape, a slit-like shape, or acheckered pattern. The opening 751H may be positioned close to anadjacent pixel. Preferably, the opening 751H is positioned close toanother pixel having a function of emitting light of the same color. Inthat case, a phenomenon in which light emitted from the second displayelement 550 enters a coloring film of the adjacent pixel (also calledcross talk), can be suppressed.

<<Second Electrode 752>>

For example, a material having a visible-light transmitting property andconductivity can be used for the second electrode 752.

For example, a conductive oxide, a metal film thin enough to transmitlight, or a metal nanowire can be used as the second electrode 752.

Specifically, a conductive oxide containing indium can be used for thesecond electrode 752. Alternatively, a metal thin film with a thicknessmore than or equal to 1 nm and less than or equal to 10 nm can be usedfor the second electrode 752. Further alternatively, a metal nanowirecontaining silver can be used for the second electrode 752.

Specifically, indium oxide, indium tin oxide, indium zinc oxide, zincoxide, zinc oxide to which gallium is added, zinc oxide to whichaluminum is added, or the like can be used for the second electrode 752.

<<Alignment Films AF1 and AF2>>

For example, the alignment films AF1 and AF2 can be formed with amaterial containing polyimide or the like. Specifically, it is possibleto use a material formed to be aligned in a predetermined direction by arubbing process or an optical alignment process.

For example, a film containing soluble polyimide can be used as thealignment film AF1 or AF2.

<<Coloring Film CF1>>

A material transmitting light of a predetermined color can be used forthe coloring film CF1. Thus, the coloring film CF1 can be used as, forexample, a color filter.

For example, a material transmitting light of blue, green, red, yellow,or white can be used for the coloring film CF1.

<<Light-Blocking Film BM>>

A material that prevents light transmission can be used for thelight-blocking film BM. Thus, the light-blocking film BM can be used as,for example, a black matrix.

<<Insulating Film 771>>

For example, polyimide, epoxy resin, acrylic resin, or the like can beused for the insulating film 771.

<<Functional Film 770P>>

For example, a polarizing plate, a retardation plate, a diffusing film,an anti-reflective film, a condensing film, or the like can be used asthe functional film 770P. Alternatively, a polarizing plate containing adichromatic pigment can be used as the functional film 770P.

Alternatively, an antistatic film preventing the attachment of dust, awater repellent film suppressing the attachment of stain, a hard coatfilm suppressing generation of a scratch in use, or the like can be usedas the functional film 770P.

<<Second Display Element 550(i, j)>>

For example, a light-emitting element can be used as the second displayelement 550(i, j). Specifically, an organic electroluminescence element,an inorganic electroluminescence element, a light-emitting diode, or thelike can be used for the second display element 550(i, j).

For example, a stack body for emitting blue light, green light, or redlight can be used as the layer 553(j) containing a light-emittingorganic compound.

For example, a stack body extending linearly in the column directionalong the signal line SI(j) can be used as the layer 553(j) containing alight-emitting organic compound. In addition, a stack body that extendslinearly in the column direction along the signal line S1(j+1) and emitslight of a color different from that of the layer 553(j) containing alight-emitting organic compound can be used as the layer 553(j+1)containing a light-emitting organic compound.

Alternatively, for example, a stack body for emitting white light can beused as the layer 553(j) containing a light-emitting organic compoundand the layer 553(j+1) containing a light-emitting organic compound.Specifically, a stack of a layer containing a light-emitting organiccompound containing a fluorescent material that emits blue light, and alayer containing a material that is other than the fluorescent materialand that emits green light and red light, or a layer containing amaterial that is other than the fluorescent material and that emitsyellow light can be used as the layer 553(j) containing a light-emittingorganic compound and the layer 553(j+1) containing a light-emittingorganic compound.

For example, a material that can be used for the wiring or the like canbe used for the third electrode 551(i, j) or the fourth electrode 552.

For example, a material that transmits visible light and is selectedfrom the materials used for the wiring or the like can be used for thethird electrode 551(i, j).

Specifically, conductive oxide, indium-containing conductive oxide,indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zincoxide to which gallium is added, or the like can be used for the thirdelectrode 551(i, j). Alternatively, a metal film that is thin enough totransmit light can be used as the third electrode 551(i, j).

For example, a material that reflects visible light and is selected fromthe materials used for the wiring or the like can be used for the fourthelectrode 552.

<<Driver Circuit GD>>

Any of a variety of sequential circuits, such as a shift register, canbe used as the driver circuit GD. For example, the transistor MD, acapacitor, and the like can be used in the driver circuit GD.Specifically, a transistor including a semiconductor film that can beformed at the same step as the transistor M can be used.

The transistor MD can have a structure different from that of thetransistor used as the switch SW1. Specifically, a transistor includingthe conductive film 524 can be used as the transistor MD (see FIG. 19C).

The semiconductor film 508 is positioned between the conductive film 504and the conductive film 524, the insulating film 516 is positionedbetween the conductive film 524 and the semiconductor film 508, and theinsulating film 506 is positioned between the semiconductor film 508 andthe conductive film 504. For example, the conductive film 524 iselectrically connected to a wiring supplying the same potential as thatsupplied to the conductive film 504.

Note that the transistor MD can have the same structure as thetransistor M.

<<Driver Circuit SD>>

For example, an integrated circuit can be used in the driver circuit SD.Specifically, an integrated circuit formed on a silicon substrate can beused as the driver circuit SD.

For example, a chip on glass (COG) method can be used to mount thedriver circuit SD on a pad electrically connected to the pixel circuit530(i, j). Specifically, an anisotropic conductive film can be used tomount the integrated circuit on the pad.

Note that the pad can be formed in the same step as the terminal 519B or519C.

<Structure Example 2 of Display Panel>

FIGS. 20A and 20B illustrate the structure of a display panel 700B ofone embodiment of the present invention. FIG. 20A is a cross-sectionalview taken along lines X1-X2, X3-X4, X5-X6, X7-X8, X9-X10, and X11-X12in FIG. 9A. FIG. 20B is a cross-sectional view illustrating part of thedisplay panel.

Note that the display panel 700B is different from the display panel 700in FIGS. 7A to 7C in including a top-gate transistor instead of thebottom-gate transistor. Described below are different structures, andthe above description is referred to for similar structures.

<<Switch SW1B, Transistor MB, Transistor MDB>>

A transistor that can be used as a switch SW1B, and transistors MB andMDB include the conductive film 504 having a region overlapping with theinsulating film 501C and the semiconductor film 508 having a regionpositioned between the insulating film 501C and the conductive film 504.Note that the conductive film 504 serves as a gate electrode (see FIG.20B).

The semiconductor film 508 includes a first region 508A, a second region508B, and a third region 508C. The first region 508A and the secondregion 508B do not overlap with the conductive film 504. The thirdregion 508C lies between the first region 508A and the second region508B and overlaps with the conductive film 504.

The transistor MDB includes the insulating film 506 between the thirdregion 508C and the conductive film 504. Note that the insulating film506 serves as a gate insulating film.

The first region 508A and the second region 508B have a lowerresistivity than the third region 508C, and serve as a source region ora drain region.

Note that the first region 508A and the second region 508B can be formedin the semiconductor film 508 by, for example, a method for controllingthe resistivity of the oxide semiconductor, which is described in detailin the end of this embodiment. Specifically, plasma treatment using agas containing a rare gas can be employed.

Furthermore, for example, the conductive film 504 can be used as a mask,in which case the shape of part of the third region 508C can be the sameas the shape of an end portion of the conductive film 504 in aself-aligned manner.

The transistor MDB includes the conductive films 512A and 512B which arein contact with the first region 508A and the second region 508B,respectively. The conductive films 512A and 512B serve as a sourceelectrode or a drain electrode.

The transistor that can be formed in the same process as the transistorMDB can be used as the transistor MB.

<Method for Controlling Resistivity of Oxide Semiconductor>

The method for controlling the resistivity of an oxide semiconductorfilm will be described.

An oxide semiconductor film with a certain resistivity can be used forthe semiconductor film 508 or the conductive film 524.

For example, the resistivity of an oxide semiconductor film can becontrolled by a method for controlling the concentration of impuritiessuch as hydrogen and water contained in the oxide semiconductor filmand/or the oxygen vacancies in the film.

Specifically, plasma treatment can be used as a method for increasing ordecreasing the concentration of impurities such as hydrogen and waterand/or the oxygen vacancies in the film.

Specifically, plasma treatment using a gas containing one or more kindsselected from a rare gas (He, Ne, Ar, Kr, Xe), hydrogen, boron,phosphorus, and nitrogen can be employed. For example, plasma treatmentin an Ar atmosphere, plasma treatment in a mixed gas atmosphere of Arand hydrogen, plasma treatment in an ammonia atmosphere, plasmatreatment in a mixed gas atmosphere of Ar and ammonia, or plasmatreatment in a nitrogen atmosphere can be employed. Thus, the oxidesemiconductor film can have a high carrier density and a lowresistivity.

Alternatively, hydrogen, boron, phosphorus, or nitrogen is added to theoxide semiconductor film by an ion implantation method, an ion dopingmethod, a plasma immersion ion implantation method, or the like, so thatthe oxide semiconductor film can have a low resistivity.

Alternatively, an insulating film containing hydrogen is formed incontact with the oxide semiconductor film, and the hydrogen is diffusedfrom the insulating film to the oxide semiconductor film, so that theoxide semiconductor film can have a high carrier density and a lowresistivity.

For example, an insulating film with a hydrogen concentration of greaterthan or equal to 1×10²² atoms/cm³ is formed in contact with the oxidesemiconductor film, in which case hydrogen can be effectively suppliedto the oxide semiconductor film. Specifically, a silicon nitride filmcan be used as the insulating film formed in contact with the oxidesemiconductor film.

Hydrogen contained in the oxide semiconductor film reacts with oxygenbonded to a metal atom to be water, and an oxygen vacancy is formed in alattice from which oxygen is released (or a portion from which oxygen isreleased). Due to entry of hydrogen into the oxygen vacancy, an electronserving as a carrier is generated in some cases. Furthermore, bonding ofpart of hydrogen to oxygen bonded to a metal atom causes generation ofan electron serving as a carrier in some cases. Thus, the oxidesemiconductor film can have a high carrier density and a lowresistivity.

Specifically, an oxide semiconductor with a hydrogen concentrationmeasured by secondary ion mass spectrometry (SIMS) of greater than orequal to 8×10¹⁹ atoms/cm³, preferably greater than or equal to 1×10²⁰atoms/cm³, more preferably greater than or equal to 5×10²⁰ atoms/cm³ canbe suitably used for the conductive film 524.

On the other hand, an oxide semiconductor with a high resistivity can beused for a semiconductor film where a channel of a transistor is formed,specifically, for the semiconductor film 508.

For example, an insulating film containing oxygen, i.e., an insulatingfilm capable of releasing oxygen, is formed in contact with an oxidesemiconductor film, and the oxygen is supplied from the insulating filmto the oxide semiconductor film, so that oxygen vacancies in the film orat the interface can be filled. Thus, the oxide semiconductor film canhave a high resistivity.

For example, a silicon oxide film or a silicon oxynitride film can beused as the insulating film capable of releasing oxygen.

The oxide semiconductor film in which oxygen vacancies are filled andthe hydrogen concentration is reduced can be referred to as a highlypurified intrinsic or substantially highly purified intrinsic oxidesemiconductor film. The term “substantially intrinsic” refers to thestate in which an oxide semiconductor film has a carrier density lowerthan 8×10¹¹/cm³, preferably lower than 1×10¹¹/cm³, further preferablylower than 1×10¹⁰/cm³. A highly purified intrinsic or substantiallyhighly purified intrinsic oxide semiconductor film has few carriergeneration sources and thus can have a low carrier density. The highlypurified intrinsic or substantially highly purified intrinsic oxidesemiconductor film has a low density of defect states and accordinglycan have a low density of trap states.

Furthermore, a transistor including the highly purified intrinsic orsubstantially highly purified intrinsic oxide semiconductor film has anextremely low off-state current; even when an element has a channelwidth of 1×10⁶ μm and a channel length L of 10 μm, the off-state currentcan be lower than or equal to the measurement limit of a semiconductorparameter analyzer, that is, lower than or equal to 1×10⁻¹³ A, at avoltage (drain voltage) between a source electrode and a drain electrodeof from 1 V to 10 V.

The transistor including a channel region formed in the oxidesemiconductor film that is a highly purified intrinsic or substantiallyhighly purified intrinsic oxide semiconductor film can have a smallchange in electrical characteristics and high reliability.

Specifically, an oxide semiconductor has a hydrogen concentration whichis measured by secondary ion mass spectrometry (SIMS) of lower than orequal to 2×10²⁰ atoms/cm³, preferably lower than or equal to 5×10¹⁹atoms/cm³, more preferably lower than or equal to 1×10¹⁹ atoms/cm³, morepreferably lower than 5×10¹⁸ atoms/cm³, more preferably lower than orequal to 1×10¹⁸ atoms/cm³, more preferably lower than or equal to 5×10¹⁷atoms/cm³, more preferably lower than or equal to 1×10¹⁶ atoms/cm³ canbe favorably used for a semiconductor where a channel of a transistor isformed.

Note that an oxide semiconductor film that has a higher hydrogenconcentration and/or a larger number of oxygen vacancies and that has alower resistivity than the semiconductor film 508 is used as theconductive film 524.

Furthermore, a film whose hydrogen concentration is twice or more,preferably ten times or more that in the semiconductor film 508 can beused as in the conductive film 524.

Moreover, a film whose resistivity is higher than or equal to 1×10⁻⁸times and lower than 1×10⁻¹ times the resistivity of the semiconductorfilm 508 can be used as the conductive film 524.

Specifically, a film with a resistivity higher than or equal to 1×10⁻³Ωcm and lower than 1×10⁴ Ωcm, preferably higher than or equal to 1×10⁻³Ωcm and lower than 1×10⁻¹ Ωcm can be used as the conductive film 524.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 5

In this embodiment, the structure of a transistor that can be used forthe display panel of one embodiment of the present invention isdescribed with reference to FIGS. 12A to 12D.

<Structure Example of Semiconductor Device>

FIG. 12A is a top view of a transistor 100. FIG. 12C is across-sectional view taken along the cutting plane line X1-X2 in FIG.12A. FIG. 12D is a cross-sectional view taken along the cutting planeline Y1-Y2 in FIG. 12A. Note that in FIG. 12A, some components of thetransistor 100 (e.g., an insulating film serving as a gate insulatingfilm) are not illustrated to avoid complexity. In some cases, thedirection of the cutting plane line X1-X2 is referred to as a channellength direction and the direction of the cutting plane line Y1-Y2 isreferred to as a channel width direction. As in FIG. 12A, somecomponents might not be illustrated in some top views of transistorsdescribed below.

Note that the transistor 100 can be used in the display panel 700 or thelike described in Embodiment 4.

For example, when the transistor 100 is used as the switch SW1, asubstrate 102, a conductive film 104, a stacked film of an insulatingfilm 106 and an insulating film 107, an oxide semiconductor film 108, aconductive film 112 a, a conductive film 112 b, a stacked film of aninsulating film 114 and an insulating film 116, and an insulating film118 can be referred to as the insulating film 501C, the conductive film504, the insulating film 506, the semiconductor film 508, the conductivefilm 512A, the conductive film 512B, the insulating film 516, and theinsulating film 518, respectively.

The transistor 100 includes the conductive film 104 functioning as agate electrode over the substrate 102, the insulating film 106 over thesubstrate 102 and the conductive film 104, the insulating film 107 overthe insulating film 106, the oxide semiconductor film 108 over theinsulating film 107, and the conductive films 112 a and 112 bfunctioning as source and drain electrodes electrically connected to theoxide semiconductor film 108. Over the transistor 100, specifically,over the conductive films 112 a and 112 b and the oxide semiconductorfilm 108, the insulating films 114, 116, and 118 are provided. Theinsulating films 114, 116, and 118 function as protective insulatingfilms for the transistor 100.

The oxide semiconductor film 108 includes a first oxide semiconductorfilm 108 a on the conductive film 104 side and a second oxidesemiconductor film 108 b over the first oxide semiconductor film 108 a.The conductive film 104 serves as a gate electrode. Furthermore, theinsulating films 106 and 107 function as gate insulating films of thetransistor 100.

An In-M oxide (M is Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf) or an In-M-Znoxide can be used for the oxide semiconductor film 108. It isparticularly preferable to use an In-M-Zn oxide for the oxidesemiconductor film 108.

The first oxide semiconductor film 108 a includes a first region inwhich the atomic proportion of In is larger than the atomic proportionof M The second oxide semiconductor film 108 b includes a second regionin which the atomic proportion of In is smaller than that in the firstoxide semiconductor film 108 a. The second region includes a portionthinner than the first region.

The first oxide semiconductor film 108 a including the first region inwhich the atomic proportion of In is larger than that of M can increasethe field-effect mobility (also simply referred to as mobility or μFE)of the transistor 100. Specifically, the field-effect mobility of thetransistor 100 can exceed 10 cm²/Vs.

For example, the use of the transistor with high field-effect mobilityfor a gate driver that generates a gate signal (specifically, ademultiplexer connected to an output terminal of a shift registerincluded in a gate driver) allows a semiconductor device or a displaydevice to have a narrow frame.

On the other hand, the first oxide semiconductor film 108 a includingthe first region in which the atomic proportion of In is larger thanthat of M makes it easier to change electrical characteristics of thetransistor 100 in light irradiation. However, in the semiconductordevice of one embodiment of the present invention, the second oxidesemiconductor film 108 b is formed over the first oxide semiconductorfilm 108 a. In addition, the thickness of the channel region in thesecond oxide semiconductor film 108 b is smaller than the thickness ofthe first oxide semiconductor film 108 a.

Furthermore, the second oxide semiconductor film 108 b includes thesecond region in which the atomic proportion of In is smaller than thatin the first oxide semiconductor film 108 a and thus has larger Eg thanthe first oxide semiconductor film 108 a. For this reason, the oxidesemiconductor film 108 that is a layered structure of the first oxidesemiconductor film 108 a and the second oxide semiconductor film 108 bhas high resistance to a negative bias stress test with lightirradiation.

The amount of light absorbed by the oxide semiconductor film 108 can bereduced during light irradiation. As a result, the change in electricalcharacteristics of the transistor 100 due to light irradiation can bereduced. In the semiconductor device of one embodiment of the presentinvention, the insulating film 114 or the insulating film 116 includesexcess oxygen. This structure can further reduce the change inelectrical characteristics of the transistor 100 due to lightirradiation.

Here, the oxide semiconductor film 108 is described in detail withreference to FIG. 12B.

FIG. 12B is a cross-sectional enlarged view of the oxide semiconductorfilm 108 and the vicinity thereof in the transistor 100 illustrated inFIG. 12C.

In FIG. 12B, t1, t2-1, and t2-2 denote a thickness of the first oxidesemiconductor film 108 a, one thickness of the second oxidesemiconductor film 108 b, and the other thickness of the second oxidesemiconductor film 108 b, respectively. The second oxide semiconductorfilm 108 b over the first oxide semiconductor film 108 a prevents thefirst oxide semiconductor film 108 a from being exposed to an etchinggas, an etchant, or the like when the conductive films 112 a and 112 bare formed. This is why the first oxide semiconductor film 108 a is notor is hardly reduced in thickness. In contrast, in the second oxidesemiconductor film 108 b, a portion not overlapping with the conductivefilms 112 a and 112 b is etched by formation of the conductive films 112a and 112 b, so that a depression is formed in the etched region. Inother words, a thickness of the second oxide semiconductor film 108 b ina region overlapping with the conductive films 112 a and 112 b is t2-1,and a thickness of the second oxide semiconductor film 108 b in a regionnot overlapping with the conductive films 112 a and 112 b is t2-2.

As for the relationships between the thicknesses of the oxidesemiconductor film 108 a and the second oxide semiconductor film 108 b,t2-1>t1>t2-2 is preferable. A transistor with the thicknessrelationships can have high field-effect mobility and less variation inthreshold voltage in light irradiation.

When oxygen vacancies are formed in the oxide semiconductor film 108included in the transistor 100, electrons serving as carriers aregenerated; as a result, the transistor 100 tends to be normally-on.Therefore, for stable transistor characteristics, it is important toreduce oxygen vacancies in the oxide semiconductor film 108,particularly oxygen vacancies in the first oxide semiconductor film 108a. In the structure of the transistor of one embodiment of the presentinvention, excess oxygen is introduced into an insulating film over theoxide semiconductor film 108, here, the insulating film 114 and/or theinsulating film 116 over the oxide semiconductor film 108, wherebyoxygen is moved from the insulating film 114 and/or the insulating film116 to the oxide semiconductor film 108 to fill oxygen vacancies in theoxide semiconductor film 108, particularly in the first oxidesemiconductor film 108 a.

Note that it is preferable that the insulating films 114 and 116 eachinclude a region (oxygen excess region) including oxygen in excess ofthat in the stoichiometric composition. In other words, the insulatingfilms 114 and 116 are insulating films capable of releasing oxygen. Notethat the oxygen excess region is formed in the insulating films 114 and116 in such a manner that oxygen is introduced into the insulating films114 and 116 after the deposition, for example. As a method forintroducing oxygen, an ion implantation method, an ion doping method, aplasma immersion ion implantation method, plasma treatment, or the likemay be employed.

In order to fill oxygen vacancies in the first oxide semiconductor film108 a, the thickness of the portion including the channel region and thevicinity of the channel region in the second oxide semiconductor film108 b is preferably small, and t2-2<t1 is preferably satisfied. Forexample, the thickness of the portion including the channel region andthe vicinity of the channel region in the second oxide semiconductorfilm 108 b is preferably more than or equal to 1 nm and less than orequal to 20 nm, further preferably more than or equal to 3 nm and lessthan or equal to 10 nm.

Other constituent elements of the semiconductor device of thisembodiment are described below in detail.

<Substrate>

There is no particular limitation on the property of a material and thelike of the substrate 102 as long as the material has heat resistanceenough to withstand at least heat treatment to be performed later. Forexample, a glass substrate, a ceramic substrate, a quartz substrate, ora sapphire substrate may be used as the substrate 102.

Alternatively, a single crystal semiconductor substrate or apolycrystalline semiconductor substrate of silicon or silicon carbide, acompound semiconductor substrate of silicon germanium, an SOI substrate,or the like can be used.

Alternatively, any of these substrates provided with a semiconductorelement, an insulating film, or the like may be used as the substrate102.

Note that in the case where a glass substrate is used as the substrate102, a large substrate having any of the following sizes can be used:the 6th generation (1500 mm×1850 mm), the 7th generation (1870 mm×2200mm), the 8th generation (2200 mm×2400 mm), the 9th generation (2400mm×2800 mm), and the 10th generation (2950 mm×3400 mm). Thus, a largedisplay device can be manufactured.

Alternatively, a flexible substrate may be used as the substrate 102,and the transistor 100 may be provided directly on the flexiblesubstrate. Alternatively, a separation layer may be provided between thesubstrate 102 and the transistor 100. The separation layer can be usedwhen part or the whole of a semiconductor device formed over theseparation layer is separated from the substrate 102 and transferredonto another substrate. In such a case, the transistor 100 can betransferred to a substrate having low heat resistance or a flexiblesubstrate as well.

<Conductive Film Functioning as Gate Electrode, Source Electrode, andDrain Electrode>

The conductive film 104 functioning as a gate electrode and theconductive films 112 a and 112 b functioning as a source electrode and adrain electrode, respectively, can each be formed using a metal elementselected from chromium (Cr), copper (Cu), aluminum (Al), gold (Au),silver (Ag), zinc (Zn), molybdenum (Mo), tantalum (Ta), titanium (Ti),tungsten (W), manganese (Mn), nickel (Ni), iron (Fe), and cobalt (Co);an alloy including any of these metal elements as its component; analloy including a combination of any of these metal elements; or thelike.

Furthermore, the conductive films 104, 112 a, and 112 b may have asingle-layer structure or a stacked-layer structure of two or morelayers. For example, a single-layer structure of an aluminum filmincluding silicon, a two-layer structure in which a titanium film isstacked over an aluminum film, a two-layer structure in which a titaniumfilm is stacked over a titanium nitride film, a two-layer structure inwhich a tungsten film is stacked over a titanium nitride film, atwo-layer structure in which a tungsten film is stacked over a tantalumnitride film or a tungsten nitride film, and a three-layer structure inwhich a titanium film, an aluminum film, and a titanium film are stackedin this order can be given. Alternatively, an alloy film or a nitridefilm in which aluminum and one or more elements selected from titanium,tantalum, tungsten, molybdenum, chromium, neodymium, and scandium arecombined may be used.

The conductive films 104, 112 a, and 112 b can be formed using alight-transmitting conductive material such as indium tin oxide, indiumoxide including tungsten oxide, indium zinc oxide including tungstenoxide, indium oxide including titanium oxide, indium tin oxide includingtitanium oxide, indium zinc oxide, or indium tin oxide to which siliconoxide is added.

A Cu—X alloy film (X is Mn, Ni, Cr, Fe, Co, Mo, Ta, or Ti) may be usedfor the conductive films 104, 112 a, and 112 b. Use of a Cu—X alloy filmenables the manufacturing cost to be reduced because wet etching processcan be used in the processing.

<Insulating Film Functioning as Gate Insulating Film>

As each of the insulating films 106 and 107 functioning as gateinsulating films of the transistor 100, an insulating film including atleast one of the following films formed by a plasma enhanced chemicalvapor deposition (PECVD) method, a sputtering method, or the like can beused: a silicon oxide film, a silicon oxynitride film, a silicon nitrideoxide film, a silicon nitride film, an aluminum oxide film, a hafniumoxide film, an yttrium oxide film, a zirconium oxide film, a galliumoxide film, a tantalum oxide film, a magnesium oxide film, a lanthanumoxide film, a cerium oxide film, and a neodymium oxide film. Note thatinstead of a stacked-layer structure of the insulating films 106 and107, an insulating film of a single layer formed using a materialselected from the above or an insulating film of three or more layersmay be used.

The insulating film 106 has a function as a blocking film that inhibitspenetration of oxygen. For example, in the case where excess oxygen issupplied to the insulating film 107, the insulating film 114, theinsulating film 116, and/or the oxide semiconductor film 108, theinsulating film 106 can inhibit penetration of oxygen.

Note that the insulating film 107 that is in contact with the oxidesemiconductor film 108 functioning as a channel region of the transistor100 is preferably an oxide insulating film and preferably includes aregion including oxygen in excess of the stoichiometric composition(oxygen-excess region). In other words, the insulating film 107 is aninsulating film capable of releasing oxygen. In order to provide theoxygen excess region in the insulating film 107, the insulating film 107is formed in an oxygen atmosphere, for example. Alternatively, theoxygen excess region may be formed by introduction of oxygen into theinsulating film 107 after the deposition. As a method for introducingoxygen, an ion implantation method, an ion doping method, a plasmaimmersion ion implantation method, plasma treatment, or the like may beemployed.

In the case where hafnium oxide is used for the insulating film 107, thefollowing effect is attained. Hafnium oxide has a higher dielectricconstant than silicon oxide and silicon oxynitride. Therefore, by usinghafnium oxide, the thickness of the insulating film 107 can be madelarge as compared with the case where silicon oxide is used; thus,leakage current due to tunnel current can be low. That is, it ispossible to provide a transistor with a low off-state current. Moreover,hafnium oxide with a crystalline structure has higher dielectricconstant than hafnium oxide with an amorphous structure. Therefore, itis preferable to use hafnium oxide with a crystalline structure in orderto provide a transistor with a low off-state current. Examples of thecrystalline structure include a monoclinic crystal structure and a cubiccrystal structure. Note that one embodiment of the present invention isnot limited thereto.

In this embodiment, a silicon nitride film is formed as the insulatingfilm 106, and a silicon oxide film is formed as the insulating film 107.The silicon nitride film has a higher dielectric constant than a siliconoxide film and needs a larger thickness for electrostatic capacitanceequivalent to that of the silicon oxide film. Thus, when the siliconnitride film is included in the gate insulating film of the transistor100, the physical thickness of the insulating film can be increased.This makes it possible to reduce a decrease in withstand voltage of thetransistor 100 and furthermore to increase the withstand voltage,thereby reducing electrostatic discharge damage to the transistor 100.

<Oxide Semiconductor Film>

The oxide semiconductor film 108 can be formed using the materialsdescribed above.

In the case where the oxide semiconductor film 108 includes In-M-Znoxide, it is preferable that the atomic ratio of metal elements of asputtering target used for forming the In-M-Zn oxide satisfy In≥M andZn≥M. As the atomic ratio of metal elements of such a sputtering target,In:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=2:1:3, In:M:Zn=3:1:2, andIn:M:Zn=4:2:4.1 are preferable.

In the case where the oxide semiconductor film 108 includes In-M-Znoxide, it is preferable to use a target including polycrystallineIn-M-Zn oxide as the sputtering target. The use of the target includingpolycrystalline In-M-Zn oxide facilitates formation of the oxidesemiconductor film 108 having crystallinity. Note that the atomic ratiosof metal elements in the formed oxide semiconductor film 108 vary fromthe above atomic ratio of metal elements of the sputtering target withina range of ±40% as an error. For example, when a sputtering target withan atomic ratio of In to Ga and Zn of 4:2:4.1 is used, the atomic ratioof In to Ga and Zn in the formed oxide semiconductor film 108 may be4:2:3 or in the vicinity of 4:2:3.

The first oxide semiconductor film 108 a can be formed using thesputtering target having an atomic ratio of In:M:Zn=2:1:3,In:M:Zn=3:1:2, or In:M:Zn=4:2:4.1. The second oxide semiconductor film108 b can be formed using the sputtering target having an atomic ratioof In:M:Zn=1:1:1 or In:M:Zn=1:1:1.2. Note that the atomic ratio of metalelements in a sputtering target used for forming the second oxidesemiconductor film 108 b does not necessarily satisfy In ≥M and Zn≥M,and may satisfy In ≥M and Zn<M, such as In:M:Zn=1:3:2.

The energy gap of the oxide semiconductor film 108 is 2 eV or more,preferably 2.5 eV or more, further preferably 3 eV or more. The use ofan oxide semiconductor having a wide energy gap can reduce off-statecurrent of the transistor 100. In particular, an oxide semiconductorfilm having an energy gap more than or equal to 2 eV, preferably morethan or equal to 2 eV and less than or equal to 3.0 eV is preferablyused as the first oxide semiconductor film 108 a, and an oxidesemiconductor film having an energy gap more than or equal to 2.5 eV andless than or equal to 3.5 eV is preferably used as the second oxidesemiconductor film 108 b. Furthermore, the second oxide semiconductorfilm 108 b preferably has a higher energy gap than that of the firstoxide semiconductor film 108 a.

Each thickness of the first oxide semiconductor film 108 a and thesecond oxide semiconductor film 108 b is more than or equal to 3 nm andless than or equal to 200 nm, preferably more than or equal to 3 nm andless than or equal to 100 nm, further preferably more than or equal to 3nm and less than or equal to 50 nm. Note that the above-describedthickness relationships between them are preferably satisfied.

An oxide semiconductor film with low carrier density is used as thesecond oxide semiconductor film 108 b. For example, the carrier densityof the second oxide semiconductor film 108 b is lower than or equal to1×10¹⁷ cm⁻³, preferably lower than or equal to 1×10¹⁵ cm⁻³, furtherpreferably lower than or equal to 1×10¹³ cm⁻³, still further preferablylower than or equal to 1×10¹¹ cm⁻³.

Note that, without limitation to the compositions and materialsdescribed above, a material with an appropriate composition may be useddepending on required semiconductor characteristics and electricalcharacteristics (e.g., field-effect mobility and threshold voltage) of atransistor. Furthermore, in order to obtain required semiconductorcharacteristics of a transistor, it is preferable that the carrierdensity, the impurity concentration, the defect density, the atomicratio of a metal element to oxygen, the interatomic distance, thedensity, and the like of the first oxide semiconductor film 108 a andthe second oxide semiconductor film 108 b be set to be appropriate.

Note that it is preferable to use, as the first oxide semiconductor film108 a and the second oxide semiconductor film 108 b, an oxidesemiconductor film in which the impurity concentration is low and thedensity of defect states is low, in which case the transistor can havemore excellent electrical characteristics. Here, the state in which theimpurity concentration is low and the density of defect states is low(the number of oxygen vacancies is small) is referred to as “highlypurified intrinsic” or “substantially highly purified intrinsic”. Ahighly purified intrinsic or substantially highly purified intrinsicoxide semiconductor film has few carrier generation sources, and thuscan have a low carrier density. Thus, a transistor in which a channelregion is formed in the oxide semiconductor film rarely has a negativethreshold voltage (is rarely normally on). A highly purified intrinsicor substantially highly purified intrinsic oxide semiconductor film hasa low density of defect states and accordingly has a low density of trapstates in some cases. Furthermore, the highly purified intrinsic orsubstantially highly purified intrinsic oxide semiconductor film has anextremely low off-state current; even when an element has a channelwidth of 1×10⁶ μm and a channel length L of 10 μm, the off-state currentcan be less than or equal to the measurement limit of a semiconductorparameter analyzer, that is, less than or equal to 1×10⁻¹³ A, at avoltage (drain voltage) between a source electrode and a drain electrodeof from 1 V to 10 V.

Accordingly, the transistor in which the channel region is formed in thehighly purified intrinsic or substantially highly purified intrinsicoxide semiconductor film can have a small change in electricalcharacteristics and high reliability. Charges trapped by the trap statesin the oxide semiconductor film take a long time to be released and maybehave like fixed charges. Thus, the transistor whose channel region isformed in the oxide semiconductor film having a high density of trapstates has unstable electrical characteristics in some cases. Asexamples of the impurities, hydrogen, nitrogen, alkali metal, alkalineearth metal, and the like are given.

Hydrogen included in the oxide semiconductor film reacts with oxygenbonded to a metal atom to be water, and also causes oxygen vacancies ina lattice from which oxygen is released (or a portion from which oxygenis released). Due to entry of hydrogen into the oxygen vacancies,electrons serving as carriers are generated in some cases. Furthermore,in some cases, bonding of part of hydrogen to oxygen bonded to a metalatom causes generation of electrons serving as carriers. Thus, atransistor including an oxide semiconductor film that contains hydrogenis likely to be normally on. Accordingly, it is preferable that hydrogenbe reduced as much as possible in the oxide semiconductor film 108.Specifically, in the oxide semiconductor film 108, the concentration ofhydrogen that is measured by SIMS is lower than or equal to 2×10²⁰atoms/cm³, preferably lower than or equal to 5×10¹⁹ atoms/cm³, furtherpreferably lower than or equal to 1×10¹⁹ atoms/cm³, further preferablylower than or equal to 5×10¹⁸ atoms/cm³, further preferably lower thanor equal to 1×10¹⁸ atoms/cm³, further preferably lower than or equal to5×10¹⁷ atoms/cm³, and further preferably lower than or equal to 1×10¹⁶atoms/cm³.

When silicon or carbon that is one of elements belonging to Group 14 isincluded in the first oxide semiconductor film 108 a, oxygen vacanciesare increased in the first oxide semiconductor film 108 a, and the firstoxide semiconductor film 108 a becomes an n-type film. Thus, theconcentration of silicon or carbon (the concentration is measured bySIMS) in the first oxide semiconductor film 108 a or the concentrationof silicon or carbon (the concentration is measured by SIMS) in thevicinity of an interface with the first oxide semiconductor film 108 ais set to be lower than or equal to 2×10¹⁸ atoms/cm³, preferably lowerthan or equal to 2×10¹⁷ atoms/cm³.

In addition, the concentration of alkali metal or alkaline earth metalof the first oxide semiconductor film 108 a, which is measured by SIMS,is lower than or equal to 1×10¹⁸ atoms/cm³, preferably lower than orequal to 2×10¹⁶ atoms/cm³. Alkali metal and alkaline earth metal mightgenerate carriers when bonded to an oxide semiconductor, in which casethe off-state current of the transistor might be increased. Therefore,it is preferable to reduce the concentration of alkali metal or alkalineearth metal of the first oxide semiconductor film 108 a.

Furthermore, when including nitrogen, the first oxide semiconductor film108 a easily becomes n-type by generation of electrons serving ascarriers and an increase of carrier density. Thus, a transistorincluding an oxide semiconductor film that contains nitrogen is likelyto have normally-on characteristics. For this reason, nitrogen in theoxide semiconductor film is preferably reduced as much as possible; theconcentration of nitrogen that is measured by SIMS is preferably set tobe, for example, lower than or equal to 5×10¹⁸ atoms/cm³.

The first oxide semiconductor film 108 a and the second oxidesemiconductor film 108 b may each have a non-single-crystal structure.The non-single crystal structure includes a c-axis aligned crystallineoxide semiconductor (CAAC-OS), a polycrystalline structure, amicrocrystalline structure, or an amorphous structure, for example.

<Insulating Film Functioning as Protective Insulating Film ofTransistor>

The insulating films 114 and 116 each have a function of supplyingoxygen to the oxide semiconductor film 108. The insulating film 118 hasa function as a protective insulating film of the transistor 100. Theinsulating films 114 and 116 include oxygen. Furthermore, the insulatingfilm 114 is an insulating film that can transmit oxygen. The insulatingfilm 114 also functions as a film that relieves damage to the oxidesemiconductor film 108 at the time of forming the insulating film 116 ina later step.

A silicon oxide film, a silicon oxynitride film, or the like with athickness greater than or equal to 5 nm and less than or equal to 150nm, preferably greater than or equal to 5 nm and less than or equal to50 nm can be used as the insulating film 114.

In addition, it is preferable that the number of defects in theinsulating film 114 be small and typically, the spin densitycorresponding to a signal that appears at g=2.001 due to a dangling bondof silicon be lower than or equal to 3×10¹⁷ spins/cm³ by electron spinresonance (ESR) measurement. This is because if the density of defectsin the insulating film 114 is high, oxygen is bonded to the defects andthe amount of oxygen that transmits the insulating film 114 isdecreased.

Note that all oxygen entering the insulating film 114 from the outsidedoes not move to the outside of the insulating film 114 and some oxygenremains in the insulating film 114. Furthermore, movement of oxygenoccurs in the insulating film 114 in some cases in such a manner thatoxygen enters the insulating film 114 and oxygen included in theinsulating film 114 moves to the outside of the insulating film 114.When an oxide insulating film that can transmit oxygen is formed as theinsulating film 114, oxygen released from the insulating film 116provided over the insulating film 114 can be moved to the oxidesemiconductor film 108 through the insulating film 114.

Note that the insulating film 114 can be formed using an oxideinsulating film having a low density of states due to nitrogen oxide.Note that the density of states due to nitrogen oxide can be formedbetween the energy of the valence band maximum (E_(v) _(_) _(os)) andthe energy of the conduction band minimum (E_(c) _(_) _(os)) of theoxide semiconductor film. A silicon oxynitride film that releases lessnitrogen oxide, an aluminum oxynitride film that releases less nitrogenoxide, and the like can be used as the above oxide insulating film.

Note that a silicon oxynitride film that releases less nitrogen oxide isa film of which the amount of released ammonia is larger than the amountof released nitrogen oxide in thermal desorption spectroscopy (TDS)analysis; the amount of released ammonia is typically greater than orequal to 1×10¹⁸ cm⁻³ and less than or equal to 5×10¹⁹ cm⁻³. Note thatthe amount of released ammonia is the amount of ammonia released by heattreatment with which the surface temperature of a film becomes higherthan or equal to 50° C. and lower than or equal to 650° C., preferablyhigher than or equal to 50° C. and lower than or equal to 550° C.

Nitrogen oxide (NO_(x); x is greater than 0 and less than or equal to 2,preferably greater than or equal to 1 and less than or equal to 2),typically NO₂ or NO, forms levels in the insulating film 114, forexample. The level is positioned in the energy gap of the oxidesemiconductor film 108. Therefore, when nitrogen oxide is diffused tothe interface between the insulating film 114 and the oxidesemiconductor film 108, an electron is in some cases trapped by thelevel on the insulating film 114 side. As a result, the trapped electronremains in the vicinity of the interface between the insulating film 114and the oxide semiconductor film 108; thus, the threshold voltage of thetransistor is shifted in the positive direction.

Nitrogen oxide reacts with ammonia and oxygen in heat treatment. Sincenitrogen oxide included in the insulating film 114 reacts with ammoniaincluded in the insulating film 116 in heat treatment, nitrogen oxideincluded in the insulating film 114 is reduced. Therefore, an electronis hardly trapped at the vicinity of the interface between theinsulating film 114 and the oxide semiconductor film 108.

By using such an oxide insulating film, the insulating film 114 canreduce the shift in the threshold voltage of the transistor, which leadsto a smaller change in the electrical characteristics of the transistor.

Note that in an ESR spectrum at 100 K or lower of the insulating film114, by heat treatment of a manufacturing process of the transistor,typically heat treatment at a temperature higher than or equal to 300°C. and lower than 350° C., a first signal that appears at a g-factor ofgreater than or equal to 2.037 and less than or equal to 2.039, a secondsignal that appears at a g-factor of greater than or equal to 2.001 andless than or equal to 2.003, and a third signal that appears at ag-factor of greater than or equal to 1.964 and less than or equal to1.966 are observed. The split width of the first and second signals andthe split width of the second and third signals that are obtained by ESRmeasurement using an X-band are each approximately 5 mT. The sum of thespin densities of the first signal that appears at a g-factor of greaterthan or equal to 2.037 and less than or equal to 2.039, the secondsignal that appears at a g-factor of greater than or equal to 2.001 andless than or equal to 2.003, and the third signal that appears at ag-factor of greater than or equal to 1.964 and less than or equal to1.966 is lower than 1×10¹⁸ spins/cm³, typically higher than or equal to1×10¹⁷ spins/cm³ and lower than 1×10¹⁸ spins/cm³.

In the ESR spectrum at 100 K or lower, the first signal that appears ata g-factor of greater than or equal to 2.037 and less than or equal to2.039, the second signal that appears at a g-factor of greater than orequal to 2.001 and less than or equal to 2.003, and the third signalthat appears at a g-factor of greater than or equal to 1.964 and lessthan or equal to 1.966 correspond to signals attributed to nitrogenoxide (NO_(x); x is greater than 0 and less than or equal to 2,preferably greater than or equal to 1 and less than or equal to 2).Typical examples of nitrogen oxide include nitrogen monoxide andnitrogen dioxide. In other words, the lower the total spin density ofthe first signal that appears at a g-factor of greater than or equal to2.037 and less than or equal to 2.039, the second signal that appears ata g-factor of greater than or equal to 2.001 and less than or equal to2.003, and the third signal that appears at a g-factor of greater thanor equal to 1.964 and less than or equal to 1.966 is, the lower thecontent of nitrogen oxide in the oxide insulating film is.

The concentration of nitrogen of the above oxide insulating filmmeasured by SIMS is lower than or equal to 6×10²⁰ atoms/cm³.

The above oxide insulating film is formed by a PECVD method at a filmsurface temperature higher than or equal to 220° C. and lower than orequal to 350° C. using silane and dinitrogen monoxide, whereby a denseand hard film can be formed.

The insulating film 116 is formed using an oxide insulating film thatcontains oxygen in excess of that in the stoichiometric composition.Part of oxygen is released by heating from the oxide insulating filmincluding oxygen in excess of that in the stoichiometric composition.The oxide insulating film including oxygen in excess of that in thestoichiometric composition is an oxide insulating film of which theamount of released oxygen converted into oxygen atoms is greater than orequal to 1.0×10¹⁹ atoms/cm³, preferably greater than or equal to3.0×10²⁰ atoms/cm³ in TDS analysis. Note that the temperature of thefilm surface in the TDS analysis is preferably higher than or equal to100° C. and lower than or equal to 700° C., or higher than or equal to100° C. and lower than or equal to 500° C.

A silicon oxide film, a silicon oxynitride film, or the like with athickness greater than or equal to 30 nm and less than or equal to 500nm, preferably greater than or equal to 50 nm and less than or equal to400 nm can be used as the insulating film 116.

It is preferable that the number of defects in the insulating film 116be small, and typically the spin density corresponding to a signal thatappears at g=2.001 due to a dangling bond of silicon be lower than1.5×10¹⁸ spins/cm³, preferably lower than or equal to 1×10¹⁸ spins/cm³by ESR measurement. Note that the insulating film 116 is provided moreapart from the oxide semiconductor film 108 than the insulating film 114is; thus, the insulating film 116 may have higher density of defectsthan the insulating film 114.

Furthermore, the insulating films 114 and 116 can be formed usinginsulating films formed of the same kinds of materials; thus, a boundarybetween the insulating films 114 and 116 cannot be clearly observed insome cases. Thus, in this embodiment, the boundary between theinsulating films 114 and 116 is shown by a dashed line. Although atwo-layer structure of the insulating films 114 and 116 is described inthis embodiment, the present invention is not limited to this. Forexample, a single-layer structure of the insulating film 114 may beemployed.

The insulating film 118 includes nitrogen. Alternatively, the insulatingfilm 118 includes nitrogen and silicon. The insulating film 118 has afunction of blocking oxygen, hydrogen, water, alkali metal, alkalineearth metal, or the like. It is possible to prevent outward diffusion ofoxygen from the oxide semiconductor film 108, outward diffusion ofoxygen included in the insulating films 114 and 116, and entry ofhydrogen, water, or the like into the oxide semiconductor film 108 fromthe outside by providing the insulating film 118. A nitride insulatingfilm, for example, can be used as the insulating film 118. The nitrideinsulating film is formed using silicon nitride, silicon nitride oxide,aluminum nitride, aluminum nitride oxide, or the like. Note that insteadof the nitride insulating film having a blocking effect against oxygen,hydrogen, water, alkali metal, alkaline earth metal, and the like, anoxide insulating film having a blocking effect against oxygen, hydrogen,water, and the like may be provided. As the oxide insulating film havinga blocking effect against oxygen, hydrogen, water, and the like, analuminum oxide film, an aluminum oxynitride film, a gallium oxide film,a gallium oxynitride film, an yttrium oxide film, an yttrium oxynitridefilm, a hafnium oxide film, a hafnium oxynitride film, and the like canbe given.

Although the variety of films such as the conductive films, theinsulating films, and the oxide semiconductor films that are describedabove can be formed by a sputtering method or a PECVD method, such filmsmay be formed by another method, e.g., a thermal chemical vapordeposition (CVD) method. Examples of the thermal CVD method include ametal organic chemical vapor deposition (MOCVD) method and an atomiclayer deposition (ALD) method.

A thermal CVD method has an advantage that no defect due to plasmadamage is generated since it does not utilize plasma for forming a film.

Deposition by a thermal CVD method may be performed in such a mannerthat a source gas and an oxidizer are supplied to the chamber at a timeso that the pressure in a chamber is set to an atmospheric pressure or areduced pressure, and react with each other in the vicinity of thesubstrate or over the substrate.

Deposition by an ALD method may be performed in such a manner that thepressure in a chamber is set to an atmospheric pressure or a reducedpressure, source gases for reaction are sequentially introduced into thechamber, and then the sequence of the gas introduction is repeated. Forexample, two or more kinds of source gases are sequentially supplied tothe chamber by switching respective switching valves (also referred toas high-speed valves). For example, a first source gas is introduced, aninert gas (e.g., argon or nitrogen) or the like is introduced at thesame time as or after the introduction of the first gas so that thesource gases are not mixed, and then a second source gas is introduced.Note that in the case where the first source gas and the inert gas areintroduced at a time, the inert gas serves as a carrier gas, and theinert gas may also be introduced at the same time as the introduction ofthe second source gas. Alternatively, the first source gas may beexhausted by vacuum evacuation instead of the introduction of the inertgas, and then the second source gas may be introduced. The first sourcegas is adsorbed on the surface of the substrate to form a first layer;then the second source gas is introduced to react with the first layer;as a result, a second layer is stacked over the first layer, so that athin film is formed. The sequence of the gas introduction is repeated aplurality of times until a desired thickness is obtained, whereby a thinfilm with excellent step coverage can be formed. The thickness of thethin film can be adjusted by the number of repetition times of thesequence of the gas introduction; therefore, an ALD method makes itpossible to accurately adjust a thickness and thus is suitable formanufacturing a minute FET.

The variety of films such as the conductive films, the insulating films,the oxide semiconductor films, and the metal oxide films in thisembodiment can be formed by a thermal CVD method such as an MOCVD methodor an ALD method. For example, in the case where an In—Ga—Zn—O film isformed, trimethylindium, trimethylgallium, and dimethylzinc are used.Note that the chemical formula of trimethylindium is In(CH₃)₃. Thechemical formula of trimethylgallium is Ga(CH₃)₃. The chemical formulaof dimethylzinc is Zn(CH₃)₂. Without limitation to the abovecombination, triethylgallium (chemical formula: Ga(C₂H₅)₃) can be usedinstead of trimethylgallium and diethylzinc (chemical formula:Zn(C₂H₅)₂) can be used instead of dimethylzinc.

For example, in the case where a hafnium oxide film is formed by adeposition apparatus using an ALD method, two kinds of gases, that is,ozone (O₃) as an oxidizer and a source gas that is obtained byvaporizing liquid containing a solvent and a hafnium precursor compound(e.g., a hafnium alkoxide or a hafnium amide such astetrakis(dimethylamide)hafnium (TDMAH)) are used. Note that the chemicalformula of tetrakis(dimethylamide)hafnium is Hf[N(CH₃)₂]₄. Examples ofanother material liquid include tetrakis(ethylmethylamide)hafnium.

For example, in the case where an aluminum oxide film is formed by adeposition apparatus using an ALD method, two kinds of gases, e.g., H₂Oas an oxidizer and a source gas that is obtained by vaporizing liquidcontaining a solvent and an aluminum precursor compound (e.g.,trimethylaluminum (TMA)) are used. Note that the chemical formula oftrimethylaluminum is Al(CH₃)₃. Examples of another material liquidinclude tris(dimethylamide)aluminum, triisobutylaluminum, and aluminumtris(2,2,6,6-tetramethyl-3,5-heptanedionate).

For example, in the case where a silicon oxide film is formed by adeposition apparatus using an ALD method, hexachlorodisilane is adsorbedon a surface where a film is to be formed, chlorine included in theadsorbate is removed, and radicals of an oxidizing gas (e.g., 02 ordinitrogen monoxide) are supplied to react with the adsorbate.

For example, in the case where a tungsten film is formed using adeposition apparatus using an ALD method, a WF₆ gas and a B₂H₆ gas aresequentially introduced a plurality of times to form an initial tungstenfilm, and then a WF₆ gas and an H₂ gas are used, so that a tungsten filmis formed. Note that a SiH₄ gas may be used instead of a B₂H₆ gas.

For example, in the case where an oxide semiconductor film, e.g., anIn—Ga—Zn—O film is formed using a deposition apparatus using an ALDmethod, an In(CH₃)₃ gas and an O₃ gas are sequentially introduced aplurality of times to form an InO layer, a GaO layer is formed using aGa(CH₃)₃ gas and an O₃ gas, and then a ZnO layer is formed using aZn(CH₃)₂ gas and an O₃ gas. Note that the order of these layers is notlimited to this example. A mixed compound layer such as an In—Ga—Olayer, an In—Zn—O layer, or a Ga—Zn—O layer may be formed by mixingthese gases. Note that although an H₂O gas that is obtained by bubblingwater with an inert gas such as Ar may be used instead of an O₃ gas, itis preferable to use an O₃ gas, which does not contain H. Furthermore,instead of an In(CH₃)₃ gas, an In(C₂H₅)₃ gas may be used. Instead of aGa(CH₃)₃ gas, a Ga(C₂H₅)₃ gas may be used. Furthermore, a Zn(CH₃)₂ gasmay be used.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 6

In this embodiment, the structure of a transistor that can be used inthe display panel of one embodiment of the present invention isdescribed with reference to FIGS. 13A to 13C.

<Structural Example of Semiconductor Device>

FIG. 13A is a top view of the transistor 100. FIG. 13B is across-sectional view taken along the cutting plane line X1-X2 in FIG.13A. FIG. 13C is a cross-sectional view taken along the cutting planeline Y1-Y2 in FIG. 13A. Note that in FIG. 13A, some components of thetransistor 100 (e.g., an insulating film serving as a gate insulatingfilm) are not illustrated to avoid complexity. Furthermore, thedirection of the cutting plane line X1-X2 may be called a channel lengthdirection, and the direction of the cutting plane line Y1-Y2 may becalled a channel width direction. As in FIG. 13A, some components arenot illustrated in some cases in top views of transistors describedbelow.

The transistor 100 can be used for the display panel 700 or the likedescribed in Embodiment 4.

For example, when the transistor 100 is used as the transistor MB or thetransistor MD, the substrate 102, the conductive film 104, a stackedfilm of the insulating film 106 and the insulating film 107, the oxidesemiconductor film 108, the conductive film 112 a, the conductive film112 b, a stacked film of the insulating film 114 and the insulating film116, the insulating film 118, and a conductive film 120 b can bereferred to as the insulating film 501C, the conductive film 504, theinsulating film 506, the semiconductor film 508, the conductive film512A, the conductive film 512B, the insulating film 516, the insulatingfilm 518, and the conductive film 524, respectively.

The transistor 100 includes the conductive film 104 functioning as afirst gate electrode over the substrate 102, the insulating film 106over the substrate 102 and the conductive film 104, the insulating film107 over the insulating film 106, the oxide semiconductor film 108 overthe insulating film 107, and the conductive films 112 a and 112 bfunctioning as source and drain electrodes electrically connected to theoxide semiconductor film 108, the insulating films 114 and 116 over theoxide semiconductor film 108 and the conductive films 112 a and 112 b, aconductive film 120 a that is over the insulating film 116 andelectrically connected to the conductive film 112 b, the conductive film120 b over the insulating film 116, and the insulating film 118 over theinsulating film 116 and the conductive films 120 a and 120 b.

The insulating films 106 and 107 function as a first gate insulatingfilm of the transistor 100. The insulating films 114 and 116 function asa second gate insulating film of the transistor 100. The insulating film118 functions as a protective insulating film of the transistor 100. Inthis specification and the like, the insulating films 106 and 107 arecollectively referred to as a first insulating film, the insulatingfilms 114 and 116 are collectively referred to as a second insulatingfilm, and the insulating film 118 is referred to as a third insulatingfilm in some cases.

The conductive film 120 b can be used as a second gate electrode of thetransistor 100.

In the case where the transistor 100 is used in a pixel portion of adisplay panel, the conductive film 120 a can be used as an electrode ofa display element, or the like.

The oxide semiconductor film 108 includes the oxide semiconductor film108 b (on the conductive film 104 side) that functions as a first gateelectrode, and an oxide semiconductor film 108 c over the oxidesemiconductor film 108 b. The oxide semiconductor films 108 b and 108 ccontain In, M (M is Al, Ga, Y, or Sn), and Zn.

The oxide semiconductor film 108 b preferably includes a region in whichthe atomic proportion of In is larger than the atomic proportion of M,for example. The oxide semiconductor film 108 c preferably includes aregion in which the atomic proportion of In is smaller than that in theoxide semiconductor film 108 b.

The oxide semiconductor film 108 b including the region in which theatomic proportion of In is larger than that of M can increase thefield-effect mobility (also simply referred to as mobility or μFE) ofthe transistor 100. Specifically, the field-effect mobility of thetransistor 100 can exceed 10 cm²/Vs, preferably exceed 30 cm²/Vs.

For example, the use of the transistor with high field-effect mobilityfor a gate driver that generates a gate signal (specifically, ademultiplexer connected to an output terminal of a shift registerincluded in a gate driver) allows a semiconductor device or a displaydevice to have a narrow frame.

On the other hand, the oxide semiconductor film 108 b including theregion in which the atomic proportion of In is larger than that of Mmakes it easier to change electrical characteristics of the transistor100 in light irradiation. However, in the semiconductor device of oneembodiment of the present invention, the oxide semiconductor film 108 cis formed over the oxide semiconductor film 108 b. Furthermore, theoxide semiconductor film 108 c including the region in which the atomicproportion of In is smaller than that in the oxide semiconductor film108 b has larger Eg than the oxide semiconductor film 108 b. For thisreason, the oxide semiconductor film 108 that is a layered structure ofthe oxide semiconductor film 108 b and the oxide semiconductor film 108c has high resistance to a negative bias stress test with lightirradiation.

Impurities such as hydrogen or moisture entering the channel region ofthe oxide semiconductor film 108, particularly the oxide semiconductorfilm 108 b adversely affect the transistor characteristics and thereforecause a problem. Moreover, it is preferable that the amount ofimpurities such as hydrogen or moisture in the channel region of theoxide semiconductor film 108 b be as small as possible. Furthermore,oxygen vacancies formed in the channel region in the oxide semiconductorfilm 108 b adversely affect the transistor characteristics and thereforecause a problem. For example, oxygen vacancies formed in the channelregion in the oxide semiconductor film 108 b are bonded to hydrogen toserve as a carrier supply source. The carrier supply source generated inthe channel region in the oxide semiconductor film 108 b causes a changein the electrical characteristics, typically, shift in the thresholdvoltage, of the transistor 100 including the oxide semiconductor film108 b. Therefore, it is preferable that the amount of oxygen vacanciesin the channel region of the oxide semiconductor film 108 b be as smallas possible.

In view of this, one embodiment of the present invention is a structurein which insulating films in contact with the oxide semiconductor film108, specifically the insulating film 107 formed under the oxidesemiconductor film 108 and the insulating films 114 and 116 formed overthe oxide semiconductor film 108 include excess oxygen. Oxygen or excessoxygen is transferred from the insulating film 107 and the insulatingfilms 114 and 116 to the oxide semiconductor film 108, whereby theoxygen vacancies in the oxide semiconductor film can be reduced. As aresult, a change in electrical characteristics of the transistor 100,particularly a change in electrical characteristics of the transistor100 due to light irradiation, can be reduced.

In one embodiment of the present invention, a manufacturing method isused in which the number of manufacturing steps is not increased or anincrease in the number of manufacturing steps is extremely small,because the insulating film 107 and the insulating films 114 and 116 aremade to contain excess oxygen. Thus, the transistor 100 can bemanufactured with high yield.

Specifically, in a step of forming the oxide semiconductor film 108 b,the oxide semiconductor film 108 b is formed by a sputtering method inan atmosphere containing an oxygen gas, whereby oxygen or excess oxygenis added to the insulating film 107 over which the oxide semiconductorfilm 108 b is formed.

Furthermore, in a step of forming the conductive films 120 a and 120 b,the conductive films 120 a and 120 b are formed by a sputtering methodin an atmosphere containing an oxygen gas, whereby oxygen or excessoxygen is added to the insulating film 116 over which the conductivefilms 120 a and 120 b are formed. Note that in some cases, oxygen orexcess oxygen is added also to the insulating film 114 and the oxidesemiconductor film 108 under the insulating film 116 when oxygen orexcess oxygen is added to the insulating film 116.

<Oxide Conductor>

Next, an oxide conductor is described. In a step of forming theconductive films 120 a and 120 b, the conductive films 120 a and 120 bserve as a protective film for suppressing release of oxygen from theinsulating films 114 and 116. The conductive films 120 a and 120 b serveas semiconductors before a step of forming the insulating film 118 andserve as conductors after the step of forming the insulating film 118.

To allow the conductive films 120 a and 120 b to serve as conductors, anoxygen vacancy is formed in the conductive films 120 a and 120 b andhydrogen is added from the insulating film 118 to the oxygen vacancy,whereby a donor level is formed in the vicinity of the conduction band.As a result, the conductivity of each of the conductive films 120 a and120 b is increased, so that the conductive films 120 a and 120 b becomeconductors. The conductive films 120 a and 120 b having becomeconductors can each be referred to as an oxide conductor. Oxidesemiconductors generally have a visible light transmitting propertybecause of their large energy gap. An oxide conductor is an oxidesemiconductor having a donor level in the vicinity of the conductionband. Therefore, the influence of absorption due to the donor level issmall in an oxide conductor, and an oxide conductor has a visible lighttransmitting property comparable to that of an oxide semiconductor.

<Components of Semiconductor Device>

Components of the semiconductor device of this embodiment are describedbelow in detail.

As materials described below, materials described in Embodiment 5 can beused.

The material that can be used for the substrate 102 described inEmbodiment 5 can be used for the substrate 102 in this embodiment.Furthermore, the materials that can be used for the insulating films 106and 107 described in Embodiment 5 can be used for the insulating films106 and 107 in this embodiment.

In addition, the materials that can be used for the conductive filmsfunctioning as the gate electrode, the source electrode, and the drainelectrode described in Embodiment 5 can be used for the conductive filmsfunctioning as the first gate electrode, the source electrode, and thedrain electrode in this embodiment.

<Oxide Semiconductor Film>

The oxide semiconductor film 108 can be formed using the materialsdescribed above.

In the case where the oxide semiconductor film 108 b includes In-M-Znoxide, it is preferable that the atomic ratio of metal elements of asputtering target used for forming the In-M-Zn oxide satisfy In>M. Theatomic ratio between metal elements in such a sputtering target is, forexample, In:M:Zn=2:1:3, In:M:Zn=3:1:2, or In:M:Zn=4:2:4.1.

In the case where the oxide semiconductor film 108 c includes In-M-Znoxide, it is preferable that the atomic ratio of metal elements of asputtering target used for forming a film of the In-M-Zn oxide satisfyIn≤M. The atomic ratio of metal elements in such a sputtering target is,for example, In:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=1:3:2,In:M:Zn=1:3:4, In:M:Zn=1:3:6, or In:M:Zn=1:4:5.

In the case where the oxide semiconductor films 108 b and 108 c includeIn-M-Zn oxide, it is preferable to use a target includingpolycrystalline In-M-Zn oxide as the sputtering target. The use of thetarget including polycrystalline In-M-Zn oxide facilitates formation ofthe oxide semiconductor films 108 b and 108 c having crystallinity. Notethat the atomic ratios of metal elements in each of the formed oxidesemiconductor films 108 b and 108 c vary from the above atomic ratio ofmetal elements of the sputtering target within a range of ±40% as anerror. For example, when a sputtering target of the oxide semiconductorfilm 108 b with an atomic ratio of In to Ga and Zn of 4:2:4.1 is used,the atomic ratio of In to Ga and Zn in the formed oxide semiconductorfilm 108 b may be 4:2:3 or in the vicinity of 4:2:3.

The energy gap of the oxide semiconductor film 108 is 2 eV or more,preferably 2.5 eV or more, further preferably 3 eV or more. The use ofan oxide semiconductor having a wide energy gap can reduce off-statecurrent of the transistor 100. In particular, an oxide semiconductorfilm having an energy gap more than or equal to 2 eV, preferably morethan or equal to 2 eV and less than or equal to 3.0 eV is preferablyused as the oxide semiconductor film 108 b, and an oxide semiconductorfilm having an energy gap more than or equal to 2.5 eV and less than orequal to 3.5 eV is preferably used as the oxide semiconductor film 108c. Furthermore, the oxide semiconductor film 108 c preferably has ahigher energy gap than the oxide semiconductor film 108 b.

Each thickness of the oxide semiconductor film 108 b and the oxidesemiconductor film 108 c is more than or equal to 3 nm and less than orequal to 200 nm, preferably more than or equal to 3 nm and less than orequal to 100 nm, further preferably more than or equal to 3 nm and lessthan or equal to 50 nm.

An oxide semiconductor film with low carrier density is used as theoxide semiconductor film 108 c. For example, the carrier density of theoxide semiconductor film 108 c is lower than or equal to 1×10¹⁷ cm⁻³,preferably lower than or equal to 1×10¹⁵ cm⁻³, further preferably lowerthan or equal to 1×10¹³ cm⁻³, still further preferably lower than orequal to 1×10¹¹ cm⁻³.

Note that, without limitation to the compositions and materialsdescribed above, a material with an appropriate composition may be useddepending on required semiconductor characteristics and electricalcharacteristics (e.g., field-effect mobility and threshold voltage) of atransistor. Furthermore, in order to obtain required semiconductorcharacteristics of a transistor, it is preferable that the carrierdensity, the impurity concentration, the defect density, the atomicratio of a metal element to oxygen, the interatomic distance, thedensity, and the like of the oxide semiconductor film 108 b and theoxide semiconductor film 108 c be set to be appropriate.

Note that it is preferable to use, as the oxide semiconductor film 108 band the oxide semiconductor film 108 c, an oxide semiconductor film inwhich the impurity concentration is low and the density of defect statesis low, in which case the transistor can have more excellent electricalcharacteristics. Here, the state in which the impurity concentration islow and the density of defect states is low (the amount of oxygenvacancy is small) is referred to as “highly purified intrinsic” or“substantially highly purified intrinsic”. A highly purified intrinsicor substantially highly purified intrinsic oxide semiconductor film hasfew carrier generation sources, and thus can have a low carrier density.Thus, a transistor in which a channel region is formed in the oxidesemiconductor film rarely has a negative threshold voltage (is rarelynormally on). A highly purified intrinsic or substantially highlypurified intrinsic oxide semiconductor film has a low density of defectstates and accordingly has a low density of trap states in some cases.Furthermore, the highly purified intrinsic or substantially highlypurified intrinsic oxide semiconductor film has an extremely lowoff-state current; even when an element has a channel width of 1×10⁶ μmand a channel length L of 10 μm, the off-state current can be less thanor equal to the measurement limit of a semiconductor parameter analyzer,that is, less Than or equal to 1×10⁻¹³ A, at a voltage (drain voltage)between a source electrode and a drain electrode of from 1 V to 10 V.

Accordingly, the transistor in which the channel region is formed in thehighly purified intrinsic or substantially highly purified intrinsicoxide semiconductor film can have a small change in electricalcharacteristics and high reliability. Charges trapped by the trap statesin the oxide semiconductor film take a long time to be released and maybehave like fixed charges. Thus, the transistor whose channel region isformed in the oxide semiconductor film having a high density of trapstates has unstable electrical characteristics in some cases. Asexamples of the impurities, hydrogen, nitrogen, alkali metal, andalkaline earth metal are given.

Hydrogen included in the oxide semiconductor film reacts with oxygenbonded to a metal atom to be water, and also causes oxygen vacancy in alattice from which oxygen is released (or a portion from which oxygen isreleased). Due to entry of hydrogen into the oxygen vacancy, an electronserving as a carrier is generated in some cases. Furthermore, in somecases, bonding of part of hydrogen to oxygen bonded to a metal atomcauses generation of an electron serving as a carrier. Thus, atransistor including an oxide semiconductor film that contains hydrogenis likely to be normally on. Accordingly, it is preferable that hydrogenbe reduced as much as possible in the oxide semiconductor film 108.Specifically, in the oxide semiconductor film 108, the concentration ofhydrogen that is measured by SIMS is lower than or equal to 2×10²⁰atoms/cm³, preferably lower than or equal to 5×10¹⁹ atoms/cm³, furtherpreferably lower than or equal to 1×10¹⁹ atoms/cm³, further preferablylower than or equal to 5×10¹⁸ atoms/cm³, further preferably lower thanor equal to 1×10¹⁸ atoms/cm³, further preferably lower than or equal to5×10¹⁷ atoms/cm³, and further preferably lower than or equal to 1×10¹⁶atoms/cm³.

The oxide semiconductor film 108 b preferably includes a region in whichhydrogen concentration is smaller than that in the oxide semiconductorfilm 108 c. A semiconductor device including the oxide semiconductorfilm 108 b having the region in which hydrogen concentration is smallerthan that in the oxide semiconductor film 108 c can be increased inreliability.

When silicon or carbon that is one of elements belonging to Group 14 isincluded in the oxide semiconductor film 108 b, oxygen vacancies areincreased in the oxide semiconductor film 108 b, and the oxidesemiconductor film 108 b becomes an n-type film. Thus, the concentrationof silicon or carbon (the concentration is measured by SIMS) in theoxide semiconductor film 108 b or the concentration of silicon or carbon(the concentration is measured by SIMS) in the vicinity of an interfacewith the oxide semiconductor film 108 b is set to be lower than or equalto 2×10¹⁸ atoms/cm³, preferably lower than or equal to 2×10¹⁷ atoms/cm³.

In addition, the concentration of alkali metal or alkaline earth metalof the oxide semiconductor film 108 b, which is measured by SIMS, islower than or equal to 1×10¹⁸ atoms/cm³, preferably lower than or equalto 2×10¹⁶ atoms/cm³. Alkali metal and alkaline earth metal mightgenerate carriers when bonded to an oxide semiconductor, in which casethe off-state current of the transistor might be increased. Therefore,it is preferable to reduce the concentration of alkali metal or alkalineearth metal of the oxide semiconductor film 108 b.

Furthermore, when including nitrogen, the oxide semiconductor film 108 beasily becomes n-type by generation of electrons serving as carriers andan increase of carrier density. Thus, a transistor including an oxidesemiconductor film that contains nitrogen is likely to have normally-oncharacteristics. For this reason, nitrogen in the oxide semiconductorfilm is preferably reduced as much as possible; the concentration ofnitrogen that is measured by SIMS is preferably set to be, for example,lower than or equal to 5×10¹⁸ atoms/cm³.

The oxide semiconductor film 108 b and the oxide semiconductor film 108c may have a non-single-crystal structure. The non-single crystalstructure includes CAAC-OS, a polycrystalline structure, amicrocrystalline structure, or an amorphous structure, for example.

<Insulating Films Functioning as Second Gate Insulating Film>

The insulating films 114 and 116 function as a second gate insulatingfilm of the transistor 100. In addition, the insulating films 114 and116 each have a function of supplying oxygen to the oxide semiconductorfilm 108. That is, the insulating films 114 and 116 contain oxygen.Furthermore, the insulating film 114 is an insulating film that cantransmit oxygen. Note that the insulating film 114 also functions as afilm that relieves damage to the oxide semiconductor film 108 at thetime of forming the insulating film 116 in a later step.

For example, the insulating films 114 and 116 described in Embodiment 5can be used as the insulating films 114 and 116 in this embodiment.

<Oxide Semiconductor Film Functioning as Conductive Film and OxideSemiconductor Film Functioning as Second Gate Electrode>

The material of the oxide semiconductor film 108 described above can beused for the conductive film 120 a functioning as a conductive film andthe conductive film 120 b functioning as the second gate electrode.

That is, the conductive film 120 a functioning as a conductive film andthe conductive film 120 b functioning as a second gate electrode containa metal element that is the same as that contained in the oxidesemiconductor film 108 (the oxide semiconductor film 108 b and the oxidesemiconductor film 108 c). For example, the conductive film 120 bfunctioning as a second gate electrode and the oxide semiconductor film108 (the oxide semiconductor film 108 b and the oxide semiconductor film108 c) contain the same metal element; thus, the manufacturing cost canbe reduced.

For example, in the case where the conductive film 120 a functioning asa conductive film and the conductive film 120 b functioning as a secondgate electrode each include In-M-Zn oxide, the atomic ratio of metalelements in a sputtering target used for forming the In-M-Zn oxidepreferably satisfies In≥M. The atomic ratio of metal elements in such asputtering target is In:M:Zn=2:1:3, In:M:Zn=3:1:2, In:M:Zn=4:2:4.1, orthe like.

The conductive film 120 a functioning as a conductive film and theconductive film 120 b functioning as a second gate electrode can eachhave a single-layer structure or a stacked-layer structure of two ormore layers. Note that in the case where the conductive film 120 a andthe conductive film 120 b each have a stacked-layer structure, thecomposition of the sputtering target is not limited to that describedabove.

<Insulating Film Functioning as Protective Insulating Film ofTransistor>

The insulating film 118 serves as a protective insulating film of thetransistor 100.

The insulating film 118 includes one or both of hydrogen and nitrogen.Alternatively, the insulating film 118 includes nitrogen and silicon.The insulating film 118 has a function of blocking oxygen, hydrogen,water, alkali metal, alkaline earth metal, or the like. It is possibleto prevent outward diffusion of oxygen from the oxide semiconductor film108, outward diffusion of oxygen included in the insulating films 114and 116, and entry of hydrogen, water, or the like into the oxidesemiconductor film 108 from the outside by providing the insulating film118.

The insulating film 118 has a function of supplying one or both ofhydrogen and nitrogen to the conductive film 120 a functioning as aconductive film and the conductive film 120 b functioning as a secondgate electrode. The insulating film 118 preferably includes hydrogen andhas a function of supplying the hydrogen to the conductive films 120 aand 120 b. The conductive films 120 a and 120 b supplied with hydrogenfrom the insulating film 118 function as conductors.

A nitride insulating film, for example, can be used as the insulatingfilm 118. The nitride insulating film is formed using silicon nitride,silicon nitride oxide, aluminum nitride, aluminum nitride oxide, or thelike.

Although the variety of films such as the conductive films, theinsulating films, and the oxide semiconductor films that are describedabove can be formed by a sputtering method or a PECVD method, such filmsmay be formed by another method, e.g., a thermal CVD method. Examples ofthe thermal CVD method include an MOCVD method and an ALD method.

A thermal CVD method has an advantage that no defect due to plasmadamage is generated since it does not utilize plasma for forming a film.

Deposition by a thermal CVD method may be performed in such a mannerthat a source gas and an oxidizer are supplied to the chamber at a timeso that the pressure in a chamber is set to an atmospheric pressure or areduced pressure, and react with each other in the vicinity of thesubstrate or over the substrate.

Deposition by an ALD method may be performed in such a manner that thepressure in a chamber is set to an atmospheric pressure or a reducedpressure, source gases for reaction are sequentially introduced into thechamber, and then the sequence of the gas introduction is repeated. Forexample, two or more kinds of source gases are sequentially supplied tothe chamber by switching respective switching valves (also referred toas high-speed valves). For example, a first source gas is introduced, aninert gas (e.g., argon or nitrogen) or the like is introduced at thesame time as or after the introduction of the first gas so that thesource gases are not mixed, and then a second source gas is introduced.Note that in the case where the first source gas and the inert gas areintroduced at a time, the inert gas serves as a carrier gas, and theinert gas may also be introduced at the same time as the introduction ofthe second source gas. Alternatively, the first source gas may beexhausted by vacuum evacuation instead of the introduction of the inertgas, and then the second source gas may be introduced. The first sourcegas is adsorbed on the surface of the substrate to form a first layer;then the second source gas is introduced to react with the first layer;as a result, a second layer is stacked over the first layer, so that athin film is formed. The sequence of the gas introduction is repeated aplurality of times until a desired thickness is obtained, whereby a thinfilm with excellent step coverage can be formed. The thickness of thethin film can be adjusted by the number of repetition times of thesequence of the gas introduction; therefore, an ALD method makes itpossible to accurately adjust a thickness and thus is suitable formanufacturing a minute FET.

The variety of films such as the conductive films, the insulating films,the oxide semiconductor films, and the metal oxide films in thisembodiment can be formed by a thermal CVD method such as an MOCVD methodor an ALD method. For example, in the case where an In—Ga—Zn—O film isformed, trimethylindium, trimethylgallium, and dimethylzinc are used.Note that the chemical formula of trimethylindium is In(CH₃)₃. Thechemical formula of trimethylgallium is Ga(CH₃)₃. The chemical formulaof dimethylzinc is Zn(CH₃)₂. Without limitation to the abovecombination, triethylgallium (chemical formula: Ga(C₂H₅)₃) can be usedinstead of trimethylgallium and diethylzinc (chemical formula:Zn(C₂H₅)₂) can be used instead of dimethylzinc.

For example, in the case where a hafnium oxide film is formed by adeposition apparatus using an ALD method, two kinds of gases, that is,ozone (O₃) as an oxidizer and a source gas that is obtained byvaporizing liquid containing a solvent and a hafnium precursor compound(e.g., a hafnium alkoxide or a hafnium amide such astetrakis(dimethylamide)hafnium (TDMAH)) are used. Note that the chemicalformula of tetrakis(dimethylamide)hafnium is Hf[N(CH₃)₂]₄. Examples ofanother material liquid include tetrakis(ethylmethylamide)hafnium.

For example, in the case where an aluminum oxide film is formed by adeposition apparatus using an ALD method, two kinds of gases, e.g., H₂Oas an oxidizer and a source gas that is obtained by vaporizing liquidcontaining a solvent and an aluminum precursor compound (e.g.,trimethylaluminum (TMA)) are used. Note that the chemical formula oftrimethylaluminum is Al(CH₃)₃. Examples of another material liquidinclude tris(dimethylamide)aluminum, triisobutylaluminum, and aluminumtris(2,2,6,6-tetramethyl-3,5-heptanedionate).

For example, in the case where a silicon oxide film is formed by adeposition apparatus using an ALD method, hexachlorodisilane is adsorbedon a surface where a film is to be formed, chlorine included in theadsorbate is removed, and radicals of an oxidizing gas (e.g., 02 ordinitrogen monoxide) are supplied to react with the adsorbate.

For example, in the case where a tungsten film is formed using adeposition apparatus using an ALD method, a WF₆ gas and a B₂H₆ gas aresequentially introduced a plurality of times to form an initial tungstenfilm, and then a WF₆ gas and an H₂ gas are used, so that a tungsten filmis formed. Note that a SiH₄ gas may be used instead of a B₂H₆ gas.

For example, in the case where an oxide semiconductor film, e.g., anIn—Ga—Zn—O film is formed using a deposition apparatus using an ALDmethod, an In(CH₃)₃ gas and an O₃ gas are sequentially introduced aplurality of times to form an InO layer, a GaO layer is formed using aGa(CH₃)₃ gas and an O₃ gas, and then a ZnO layer is formed using aZn(CH₃)₂ gas and an O₃ gas. Note that the order of these layers is notlimited to this example. A mixed compound layer such as an In—Ga—Olayer, an In—Zn—O layer, or a Ga—Zn—O layer may be formed by mixingthese gases. Note that although an H₂O gas that is obtained by bubblingwater with an inert gas such as Ar may be used instead of an O₃ gas, itis preferable to use an O₃ gas, which does not contain H. Furthermore,instead of an In(CH₃)₃ gas, an In(C₂H₅)₃ gas may be used. Instead of aGa(CH₃)₃ gas, a Ga(C₂H₅)₃ gas may be used. Furthermore, a Zn(CH₃)₂ gasmay be used.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 7

In this embodiment, a structure of an input/output device which is oneembodiment of the present invention will be described with reference toFIG. 14.

FIG. 14 is an exploded view of a structure of an input/output device800.

The input/output device 800 includes a display panel 806 and a touchsensor 804 having a region overlapping with the display panel 806. Notethat the input/output device 800 can be referred to as a touch panel.

The input/output device 800 is provided with a driver circuit 810 fordriving the touch sensor 804 and the display panel 806, a battery 811for supplying power to the driver circuit 810, and a housing where thetouch sensor 804, the display panel 806, the driver circuit 810, and thebattery 811 are stored.

<<Touch Sensor 804>>

The touch sensor 804 includes a region overlapping with the displaypanel 806. Note that an FPC 803 is electrically connected to the touchsensor 804.

For the touch sensor 804, a resistive touch sensor, a capacitive touchsensor, or a touch sensor using a photoelectric conversion element canbe used, for example.

Note that the touch sensor 804 may be used as part of the display panel806.

<<Display Panel 806>>

For example, the display panel described in Embodiment 1 can be used asthe display panel 806. Note that an FPC 805 or the like is electricallyconnected to the display panel 806.

<<Driver Circuit 810>>

As the driver circuit 810, a power supply circuit or a signal processingcircuit can be used, for example. Power supplied to the battery or anexternal commercial power supply can be utilized.

The signal processing circuit has a function of outputting a videosignal, a clock signal, and the like.

The power supply circuit has a function of supplying predeterminedpower.

<<Housing>>

An upper cover 801, a lower cover 802 which fits the upper cover 801,and a frame 809 which is stored in a region surrounded by the uppercover 801 and the lower cover 802 can be used for the housing, forexample.

The frame 809 has a function of protecting the display panel 806, afunction of blocking electromagnetic waves generated by the operation ofthe driver circuit 810, or a function as a radiator plate.

Metal, a resin, an elastomer, or the like can be used for the uppercover 801, the lower cover 802, or the frame 809.

<<Battery 811>>

The battery 811 has a function of supplying power.

Note that a member such as a polarizing plate, a retardation plate, or aprism sheet can be used for the input/output device 800.

This embodiment can be combined with any of the other embodiments inthis specification as appropriate.

Embodiment 8

In this embodiment, a semiconductor device (memory device) that canretain stored data even when not powered and that has an unlimitednumber of write cycles, and a CPU including the semiconductor device aredescribed. The CPU described in this embodiment can be used for the dataprocessing device described in Embodiment 1, for example.

<Memory Device>

An example of a semiconductor device (memory device) that can retainstored data even when not powered and that has an unlimited number ofwrite cycles is shown in FIGS. 15A to 15C. Note that FIG. 15B is acircuit diagram of the structure in FIG. 15A.

The semiconductor device illustrated in FIGS. 15A and 15B includes atransistor 3200 using a first semiconductor material, a transistor 3300using a second semiconductor material, and a capacitor 3400.

The first and second semiconductor materials preferably have differentenergy gaps. For example, the first semiconductor material can be asemiconductor material other than an oxide semiconductor (examples ofsuch a semiconductor material include silicon (including strainedsilicon), germanium, silicon germanium, silicon carbide, galliumarsenide, aluminum gallium arsenide, indium phosphide, gallium nitride,and an organic semiconductor), and the second semiconductor material canbe an oxide semiconductor. A transistor using a material other than anoxide semiconductor, such as single crystal silicon, can operate at highspeed easily. On the other hand, a transistor including an oxidesemiconductor has a low off-state current.

The transistor 3300 is a transistor in which a channel is formed in asemiconductor layer including an oxide semiconductor. Since theoff-state current of the transistor 3300 is small, stored data can beretained for a long period. In other words, power consumption can besufficiently reduced because a semiconductor memory device in whichrefresh operation is unnecessary or the frequency of refresh operationis extremely low can be provided.

In FIG. 15B, a first wiring 3001 is electrically connected to a sourceelectrode of the transistor 3200. A second wiring 3002 is electricallyconnected to a drain electrode of the transistor 3200. A third wiring3003 is electrically connected to one of a source electrode and a drainelectrode of the transistor 3300. A fourth wiring 3004 is electricallyconnected to a gate electrode of the transistor 3300. A gate electrodeof the transistor 3200 and the other of the source electrode and thedrain electrode of the transistor 3300 are electrically connected to oneelectrode of the capacitor 3400. A fifth wiring 3005 is electricallyconnected to the other electrode of the capacitor 3400.

The semiconductor device in FIG. 15A has a feature that the potential ofthe gate electrode of the transistor 3200 can be retained, and thusenables writing, retaining, and reading of data as follows.

Writing and retaining of data are described. First, the potential of thefourth wiring 3004 is set to a potential at which the transistor 3300 isturned on, so that the transistor 3300 is turned on. Accordingly, thepotential of the third wiring 3003 is supplied to the gate electrode ofthe transistor 3200 and the capacitor 3400. That is, a predeterminedcharge is supplied to the gate electrode of the transistor 3200(writing). Here, one of two kinds of charges providing differentpotential levels (hereinafter referred to as a low-level charge and ahigh-level charge) is supplied. After that, the potential of the fourthwiring 3004 is set to a potential at which the transistor 3300 is turnedoff, so that the transistor 3300 is turned off. Thus, the chargesupplied to the gate electrode of the transistor 3200 is held(retaining).

Since the off-state current of the transistor 3300 is extremely small,the charge of the gate electrode of the transistor 3200 is retained fora long time.

Next, reading of data is described. An appropriate potential (a readingpotential) is supplied to the fifth wiring 3005 while a predeterminedpotential (a constant potential) is supplied to the first wiring 3001,whereby the potential of the second wiring 3002 varies depending on theamount of charge retained in the gate electrode of the transistor 3200.This is because in the case of using an n-channel transistor as thetransistor 3200, an apparent threshold voltage V_(th) _(_) _(H) at thetime when the high-level charge is given to the gate electrode of thetransistor 3200 is lower than an apparent threshold voltage V_(th) _(_)_(L) at the time when the low-level charge is given to the gateelectrode of the transistor 3200. Here, an apparent threshold voltagerefers to the potential of the fifth wiring 3005 that is needed to turnon the transistor 3200. Thus, the potential of the fifth wiring 3005 isset to a potential V₀ that is between V_(th) _(_) _(H) and V_(th) _(_)_(L), whereby charge supplied to the gate electrode of the transistor3200 can be determined. For example, in the case where the high-levelcharge is supplied to the gate electrode of the transistor 3200 inwriting and the potential of the fifth wiring 3005 is V₀ (>V_(th) _(_)_(H)), the transistor 3200 is turned on. In the case where the low-levelcharge is supplied to the gate electrode of the transistor 3200 inwriting, even when the potential of the fifth wiring 3005 is V₀ (<V_(th)_(_) _(L)), the transistor 3200 remains off. Thus, the data retained inthe gate electrode of the transistor 3200 can be read by determining thepotential of the second wiring 3002.

Note that in the case where memory cells are arrayed, it is necessarythat only data of a designated memory cell(s) can be read. In the casewhere data is not read, the fifth wiring 3005 may be supplied with apotential at which the transistor 3200 is turned off regardless of thestate of the gate, that is, a potential lower than V_(th) _(_) _(H).

The semiconductor device illustrated in FIG. 15C is different from thesemiconductor device illustrated in FIG. 15A in that the transistor 3200is not provided. Also in this case, writing and retaining operation ofdata can be performed in a manner similar to those of the semiconductordevice illustrated in FIG. 15A.

Next, reading of data of the semiconductor device illustrated in FIG.15C is described. When the transistor 3300 is turned on, the thirdwiring 3003 that is in a floating state and the capacitor 3400 areelectrically connected to each other, and the charge is redistributedbetween the third wiring 3003 and the capacitor 3400. As a result, thepotential of the third wiring 3003 is changed. The amount of change inthe potential of the third wiring 3003 varies depending on the potentialof the one electrode of the capacitor 3400 (or the charge accumulated inthe capacitor 3400).

For example, the potential of the third wiring 3003 after the chargeredistribution is (C_(B)×V_(B0)+C×V)/(C_(B)+C), where V is the potentialof the one electrode of the capacitor 3400, C is the capacitance of thecapacitor 3400, C_(B) is the capacitance component of the third wiring3003, and V_(B0) is the potential of the third wiring 3003 before thecharge redistribution. Thus, it can be found that, assuming that thememory cell is in either of two states in which the potential of the oneelectrode of the capacitor 3400 is V₁ and V₀ (V₁>V₀), the potential ofthe third wiring 3003 in the case of retaining the potential V₁(=(C_(B)×V_(B0)+C×V₁)/(C_(B)+C)) is higher than the potential of thethird wiring 3003 in the case of retaining the potential V₀(=(C_(B)×V_(B0)+C×V₀)/(C_(B)+C)).

Then, by comparing the potential of the third wiring 3003 with apredetermined potential, data can be read.

In this case, a transistor including the first semiconductor materialmay be used for a driver circuit for driving a memory cell, and atransistor including the second semiconductor material may be stackedover the driver circuit as the transistor 3300.

When including a transistor in which a channel formation region isformed using an oxide semiconductor and which has an extremely smalloff-state current, the semiconductor device described in this embodimentcan retain stored data for an extremely long time. In other words,refresh operation becomes unnecessary or the frequency of the refreshoperation can be extremely low, which leads to a sufficient reduction inpower consumption. Moreover, stored data can be retained for a long timeeven when power is not supplied (note that a potential is preferablyfixed).

Furthermore, in the semiconductor device described in this embodiment,high voltage is not needed for writing data and there is no problem ofdeterioration of elements. Unlike in a conventional nonvolatile memory,for example, it is not necessary to inject and extract electrons intoand from a floating gate; thus, a problem such as deterioration of agate insulating film is not caused. That is, the semiconductor devicedescribed in this embodiment does not have a limit on the number oftimes data can be rewritten, which is a problem of a conventionalnonvolatile memory, and the reliability thereof is drastically improved.Furthermore, data is written depending on the state of the transistor(on or off), whereby high-speed operation can be easily achieved.

The above memory device can also be used in an LSI such as a digitalsignal processor (DSP), a custom LSI, or a programmable logic device(PLD) and a radio frequency identification (RF-ID) tag, in addition to acentral processing unit (CPU), for example.

<CPU>

A CPU including the above memory device is described below.

FIG. 16 is a block diagram illustrating a structural example of the CPUincluding the above memory device.

The CPU illustrated in FIG. 16 includes, over a substrate 1190, anarithmetic logic unit (ALU) 1191, an ALU controller 1192, an instructiondecoder 1193, an interrupt controller 1194, a timing controller 1195, aregister 1196, a register controller 1197, a bus interface (BUS I/F)1198, a rewritable ROM 1199, and a ROM interface (ROM I/F) 1189. Asemiconductor substrate, an SOI substrate, a glass substrate, or thelike is used as the substrate 1190. The ROM 1199 and the ROM interface1189 may be provided over a separate chip. Needless to say, the CPU inFIG. 16 is just an example in which the structure is simplified, and anactual CPU may have a variety of structures depending on theapplication. For example, the CPU may have the following structure: astructure including the CPU illustrated in FIG. 16 or an arithmeticcircuit is considered as one core; a plurality of such cores areincluded; and the cores operate in parallel. The number of bits that theCPU can process in an internal arithmetic circuit or in a data bus canbe, for example, 8, 16, 32, or 64.

An instruction that is input to the CPU through the bus interface 1198is input to the instruction decoder 1193 and decoded therein, and then,input to the ALU controller 1192, the interrupt controller 1194, theregister controller 1197, and the timing controller 1195.

The ALU controller 1192, the interrupt controller 1194, the registercontroller 1197, and the timing controller 1195 conduct various controlsin accordance with the decoded instruction. Specifically, the ALUcontroller 1192 generates signals for controlling the operation of theALU 1191. While the CPU is executing a program, the interrupt controller1194 processes an interrupt request from an external input/output deviceor a peripheral circuit depending on its priority or a mask state. Theregister controller 1197 generates an address of the register 1196, andreads/writes data from/to the register 1196 depending on the state ofthe CPU.

The timing controller 1195 generates signals for controlling operationtimings of the ALU 1191, the ALU controller 1192, the instructiondecoder 1193, the interrupt controller 1194, and the register controller1197. For example, the timing controller 1195 includes an internal clockgenerator for generating an internal clock signal on the basis of areference clock signal, and supplies the internal clock signal to theabove circuits.

In the CPU illustrated in FIG. 16, a memory cell is provided in theregister 1196.

In the CPU illustrated in FIG. 16, the register controller 1197 selectsoperation of retaining data in the register 1196 in accordance with aninstruction from the ALU 1191. That is, the register controller 1197selects whether data is retained by a flip-flop or by a capacitor in thememory cell included in the register 1196. When data retaining by theflip-flop is selected, a power supply voltage is supplied to the memorycell in the register 1196. When data retaining by the capacitor isselected, the data is rewritten in the capacitor, and supply of thepower supply voltage to the memory cell in the register 1196 can bestopped.

FIG. 17 is an example of a circuit diagram of a memory element that canbe used for the register 1196. A memory element 1200 includes a circuit1201 in which stored data is volatile when power supply is stopped, acircuit 1202 in which stored data is nonvolatile even when power supplyis stopped, a switch 1203, a switch 1204, a logic element 1206, acapacitor 1207, and a circuit 1220 having a selecting function. Thecircuit 1202 includes a capacitor 1208, a transistor 1209, and atransistor 1210. Note that the memory element 1200 may further includeanother element such as a diode, a resistor, or an inductor, as needed.

Here, the above-described memory device can be used as the circuit 1202.When supply of a power supply voltage to the memory element 1200 isstopped, a ground potential (0 V) or a potential at which the transistor1209 in the circuit 1202 is turned off continues to be input to a gateof the transistor 1209. For example, the gate of the transistor 1209 isgrounded through a load such as a resistor.

Shown here is an example in which the switch 1203 is a transistor 1213having one conductivity type (e.g., an n-channel transistor) and theswitch 1204 is a transistor 1214 having a conductivity type opposite tothe one conductivity type (e.g., a p-channel transistor). A firstterminal of the switch 1203 corresponds to one of a source and a drainof the transistor 1213, a second terminal of the switch 1203 correspondsto the other of the source and the drain of the transistor 1213, andconduction or non-conduction between the first terminal and the secondterminal of the switch 1203 (i.e., the on/off state of the transistor1213) is selected by a control signal RD input to a gate of thetransistor 1213. A first terminal of the switch 1204 corresponds to oneof a source and a drain of the transistor 1214, a second terminal of theswitch 1204 corresponds to the other of the source and the drain of thetransistor 1214, and conduction or non-conduction between the firstterminal and the second terminal of the switch 1204 (i.e., the on/offstate of the transistor 1214) is selected by the control signal RD inputto a gate of the transistor 1214.

One of a source and a drain of the transistor 1209 is electricallyconnected to one of a pair of electrodes of the capacitor 1208 and agate of the transistor 1210. Here, the connection portion is referred toas a node M2. One of a source and a drain of the transistor 1210 iselectrically connected to a wiring that can supply a low power supplypotential (e.g., a GND line), and the other thereof is electricallyconnected to the first terminal of the switch 1203 (the one of thesource and the drain of the transistor 1213). The second terminal of theswitch 1203 (the other of the source and the drain of the transistor1213) is electrically connected to the first terminal of the switch 1204(the one of the source and the drain of the transistor 1214). The secondterminal of the switch 1204 (the other of the source and the drain ofthe transistor 1214) is electrically connected to a wiring that cansupply a power supply potential VDD. The second terminal of the switch1203 (the other of the source and the drain of the transistor 1213), thefirst terminal of the switch 1204 (the one of the source and the drainof the transistor 1214), an input terminal of the logic element 1206,and one of a pair of electrodes of the capacitor 1207 are electricallyconnected to each other. Here, the connection portion is referred to asa node M1. The other of the pair of electrodes of the capacitor 1207 canbe supplied with a constant potential. For example, the other of thepair of electrodes of the capacitor 1207 can be supplied with a lowpower supply potential (e.g., GND) or a high power supply potential(e.g., VDD). The other of the pair of electrodes of the capacitor 1207is electrically connected to the wiring that can supply a low powersupply potential (e.g., a GND line). The other of the pair of electrodesof the capacitor 1208 can be supplied with a constant potential. Forexample, the other of the pair of electrodes of the capacitor 1208 canbe supplied with a low power supply potential (e.g., GND) or a highpower supply potential (e.g., VDD). The other of the pair of electrodesof the capacitor 1208 is electrically connected to the wiring that cansupply a low power supply potential (e.g., a GND line).

The capacitor 1207 and the capacitor 1208 are not necessarily providedas long as the parasitic capacitance of the transistor, the wiring, orthe like is actively utilized.

A control signal WE is input to a first gate (first gate electrode) ofthe transistor 1209. As for each of the switch 1203 and the switch 1204,a conduction state or a non-conduction state between the first terminaland the second terminal is selected by the control signal RD that isdifferent from the control signal WE. When the first terminal and thesecond terminal of one of the switches are in the conduction state, thefirst terminal and the second terminal of the other of the switches arein the non-conduction state.

A signal corresponding to data retained in the circuit 1201 is input tothe other of the source and the drain of the transistor 1209. FIG. 17illustrates an example in which a signal output from the circuit 1201 isinput to the other of the source and the drain of the transistor 1209.The logic value of a signal output from the second terminal of theswitch 1203 (the other of the source and the drain of the transistor1213) is inverted by the logic element 1206, and the inverted signal isinput to the circuit 1201 through the circuit 1220.

In the example of FIG. 17, a signal output from the second terminal ofthe switch 1203 (the other of the source and the drain of the transistor1213) is input to the circuit 1201 through the logic element 1206 andthe circuit 1220; however, one embodiment of the present invention isnot limited thereto. The signal output from the second terminal of theswitch 1203 (the other of the source and the drain of the transistor1213) may be input to the circuit 1201 without its logic value beinginverted. For example, in the case where the circuit 1201 includes anode in which a signal obtained by inversion of the logic value of asignal input from the input terminal is retained, the signal output fromthe second terminal of the switch 1203 (the other of the source and thedrain of the transistor 1213) can be input to the node.

In FIG. 17, the transistors included in the memory element 1200 exceptfor the transistor 1209 can each be a transistor in which a channel isformed in a layer formed using a semiconductor other than an oxidesemiconductor or in the substrate 1190. For example, the transistor canbe a transistor whose channel is formed in a silicon layer or a siliconsubstrate. Alternatively, a transistor in which a channel is formed inan oxide semiconductor film can be used for all the transistors in thememory element 1200. Further alternatively, in the memory element 1200,a transistor in which a channel is formed in an oxide semiconductor filmcan be included besides the transistor 1209, and a transistor in which achannel is formed in a layer formed using a semiconductor other than anoxide semiconductor or the substrate 1190 can be used for the rest ofthe transistors.

As the circuit 1201 in FIG. 17, for example, a flip-flop circuit can beused. As the logic element 1206, for example, an inverter or a clockedinverter can be used.

In a period during which the memory element 1200 is not supplied withthe power supply voltage, the semiconductor device described in thisembodiment can retain data stored in the circuit 1201 by the capacitor1208 that is provided in the circuit 1202.

The off-state current of a transistor in which a channel is formed in anoxide semiconductor film is extremely small. For example, the off-statecurrent of a transistor in which a channel is formed in an oxidesemiconductor film is significantly smaller than that of a transistor inwhich a channel is formed in silicon having crystallinity. Thus, whenthe transistor in which a channel is formed in an oxide semiconductorfilm is used as the transistor 1209, a signal is retained in thecapacitor 1208 for a long time also in a period during which the powersupply voltage is not supplied to the memory element 1200. The memoryelement 1200 can accordingly retain the stored content (data) also in aperiod during which the supply of the power supply voltage is stopped.

Since the memory element performs pre-charge operation with the switch1203 and the switch 1204, the time required for the circuit 1201 toretain original data again after the supply of the power supply voltageis restarted can be shortened.

In the circuit 1202, a signal retained by the capacitor 1208 is input tothe gate of the transistor 1210. Thus, after supply of the power supplyvoltage to the memory element 1200 is restarted, the state (the on stateor the off state) of the transistor 1210 is determined in accordancewith the signal retained by the capacitor 1208 and can be read from thecircuit 1202. Consequently, an original signal can be accurately readeven when a potential corresponding to the signal retained by thecapacitor 1208 changes to some degree.

By using the above-described memory element 1200 in a memory device suchas a register or a cache memory included in a processor, data in thememory device can be prevented from being lost owing to the stop of thesupply of the power supply voltage. Furthermore, shortly after thesupply of the power supply voltage is restarted, the memory device canbe returned to the same state as that before the power supply isstopped. Thus, the power supply can be stopped even for a short time inthe processor or one or a plurality of logic circuits included in theprocessor, resulting in lower power consumption.

Although the memory element 1200 is used in a CPU in this embodiment,the memory element 1200 can also be used in an LSI such as a digitalsignal processor (DSP), a custom LSI, or a programmable logic device(PLD), and a radio frequency identification (RF-ID) tag.

At least part of this embodiment can be implemented in combination withany of the other embodiments described in this specification asappropriate.

Embodiment 9

In this embodiment, a display module and electronic devices that includean information processing device of one embodiment of the presentinvention are described with reference to FIGS. 18A to 18H.

FIGS. 18A to 18G illustrate electronic devices. These electronic devicescan include a housing 5000, a display portion 5001, a speaker 5003, anLED lamp 5004, operation keys 5005 (including a power switch and anoperation switch), a connection terminal 5006, a sensor 5007 (a sensorhaving a function of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, odor, or infrared ray), amicrophone 5008, and the like.

FIG. 18A illustrates a mobile computer that can include a switch 5009,an infrared port 5010, and the like in addition to the above components.FIG. 18B illustrates a portable image reproducing device (e.g., a DVDreproducing device) provided with a recording medium, and the portableimage reproducing device can include a second display portion 5002, arecording medium reading portion 5011, and the like in addition to theabove components. FIG. 18C illustrates a goggle-type display that caninclude the second display portion 5002, a support portion 5012, anearphone 5013, and the like in addition to the above components. FIG.18D illustrates a portable game console that can include the recordingmedium reading portion 5011 and the like in addition to the abovecomponents. FIG. 18E illustrates a digital camera with a televisionreception function, and the digital camera can include an antenna 5014,a shutter button 5015, an image receiving portion 5016, and the like inaddition to the above components. FIG. 18F illustrates a portable gameconsole that can include the second display portion 5002, the recordingmedium reading portion 5011, and the like in addition to the abovecomponents. FIG. 18G illustrates a portable television receiver that caninclude a charger 5017 capable of transmitting and receiving signals,and the like in addition to the above components.

The electronic devices in FIGS. 18A to 18G can have a variety offunctions such as a function of displaying a variety of data (e.g., astill image, a moving image, and a text image) on the display portion, atouch panel function, a function of displaying a calendar, date, time,and the like, a function of controlling processing with a variety ofsoftware (programs), a wireless communication function, a function ofbeing connected to a variety of computer networks with a wirelesscommunication function, a function of transmitting and receiving avariety of data with a wireless communication function, and a functionof reading out a program or data stored in a recording medium anddisplaying it on the display portion. Furthermore, the electronic deviceincluding a plurality of display portions can have a function ofdisplaying image data mainly on one display portion while displayingtext data mainly on another display portion, a function of displaying athree-dimensional image by displaying images on a plurality of displayportions with a parallax taken into account, or the like. Furthermore,the electronic device including an image receiving portion can have afunction of shooting a still image, a function of taking moving images,a function of automatically or manually correcting a shot image, afunction of storing a shot image in a recording medium (an externalrecording medium or a recording medium incorporated in the camera), afunction of displaying a shot image on the display portion, or the like.Note that functions of the electronic devices in FIGS. 18A to 18G arenot limited thereto, and the electronic devices can have a variety offunctions.

FIG. 18H illustrates a smart watch, which includes a housing 7302, adisplay panel 7304, operation buttons 7311 and 7312, a connectionterminal 7313, a band 7321, a clasp 7322, and the like.

The display panel 7304 mounted in the housing 7302 serving as a bezelincludes a non-rectangular display region. The display panel 7304 mayhave a rectangular display region. The display panel 7304 can display anicon 7305 indicating time, another icon 7306, and the like.

The smart watch in FIG. 18H can have a variety of functions such as afunction of displaying a variety of data (e.g., a still image, a movingimage, and a text image) on the display portion, a touch panel function,a function of displaying a calendar, date, time, and the like, afunction of controlling processing with a variety of software(programs), a wireless communication function, a function of beingconnected to a variety of computer networks with a wirelesscommunication function, a function of transmitting and receiving avariety of data with a wireless communication function, and a functionof reading out a program or data stored in a recording medium anddisplaying it on the display portion.

The housing 7302 can include a speaker, a sensor (a sensor having afunction of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, odor, or infrared rays), amicrophone, and the like. Note that the smart watch can be manufacturedusing the light-emitting element for the display panel 7304.

This embodiment can be combined with any of the other embodiments inthis specification as appropriate.

In this specification and the like, an explicit description “X and Y areconnected” means that X and Y are electrically connected, X and Y arefunctionally connected, and X and Y are directly connected. Accordingly,without being limited to a predetermined connection relationship, forexample, a connection relationship shown in drawings or texts, anotherconnection relationship is included in the drawings or the texts.

Here, X and Y each denote an object (e.g., a device, an element, acircuit, a wiring, an electrode, a terminal, a conductive film, or alayer).

Examples of the case where X and Y are directly connected include thecase where an element that allows an electrical connection between X andY (e.g., a switch, a transistor, a capacitor, an inductor, a resistor, adiode, a display element, a light-emitting element, or a load) is notconnected between X and Y, and the case where X and Y are connectedwithout the element that allows the electrical connection between X andY provided therebetween.

For example, in the case where X and Y are electrically connected, oneor more elements that enable an electrical connection between X and Y(e.g., a switch, a transistor, a capacitor, an inductor, a resistor, adiode, a display element, a light-emitting element, or a load) can beconnected between X and Y. Note that the switch is controlled to beturned on or off. That is, the switch is conducting or not conducting(is turned on or off) to determine whether current flows therethrough ornot. Alternatively, the switch has a function of selecting and changinga current path. Note that the case where X and Y are electricallyconnected includes the case where X and Y are directly connected.

For example, in the case where X and Y are functionally connected, oneor more circuits that enable a functional connection between X and Y(e.g., a logic circuit such as an inverter, a NAND circuit, or a NORcircuit; a signal converter circuit such as a D/A converter circuit, anA/D converter circuit, or a gamma correction circuit; a potential levelconverter circuit such as a power supply circuit (e.g., a step-upcircuit or a step-down circuit) or a level shifter circuit for changingthe potential level of a signal; a voltage source; a current source; aswitching circuit; an amplifier circuit such as a circuit that canincrease signal amplitude, the amount of current, or the like, anoperational amplifier, a differential amplifier circuit, a sourcefollower circuit, and a buffer circuit; a signal generation circuit; amemory circuit; or a control circuit) can be connected between X and Y.For example, even when another circuit is interposed between X and Y, Xand Y are functionally connected if a signal output from X istransmitted to Y. Note that the case where X and Y are functionallyconnected includes the case where X and Y are directly connected and thecase where X and Y are electrically connected.

Note that in this specification and the like, an explicit description “Xand Y are electrically connected” means that X and Y are electricallyconnected (i.e., the case where X and Y are connected with anotherelement or another circuit provided therebetween), X and Y arefunctionally connected (i.e., the case where X and Y are functionallyconnected with another circuit provided therebetween), and X and Y aredirectly connected (i.e., the case where X and Y are connected withoutanother element or another circuit provided therebetween). That is, inthis specification and the like, the explicit description “X and Y areelectrically connected” is the same as the description “X and Y areconnected”.

For example, any of the following expressions can be used for the casewhere a source (or a first terminal or the like) of a transistor iselectrically connected to X through (or not through) Z1 and a drain (ora second terminal or the like) of the transistor is electricallyconnected to Y through (or not through) Z2, or the case where a source(or a first terminal or the like) of a transistor is directly connectedto one part of Z1 and another part of Z1 is directly connected to Xwhile a drain (or a second terminal or the like) of the transistor isdirectly connected to one part of Z2 and another part of Z2 is directlyconnected to Y.

Examples of the expressions include, “X, Y, a source (or a firstterminal or the like) of a transistor, and a drain (or a second terminalor the like) of the transistor are electrically connected to each other,and X, the source (or the first terminal or the like) of the transistor,the drain (or the second terminal or the like) of the transistor, and Yare electrically connected to each other in this order”, “a source (or afirst terminal or the like) of a transistor is electrically connected toX, a drain (or a second terminal or the like) of the transistor iselectrically connected to Y, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are electrically connected to each otherin this order”, and “X is electrically connected to Y through a source(or a first terminal or the like) and a drain (or a second terminal orthe like) of a transistor, and X, the source (or the first terminal orthe like) of the transistor, the drain (or the second terminal or thelike) of the transistor, and Y are provided to be connected in thisorder”. When the connection order in a circuit configuration is definedby an expression similar to the above examples, a source (or a firstterminal or the like) and a drain (or a second terminal or the like) ofa transistor can be distinguished from each other to specify thetechnical scope.

Other examples of the expressions include, “a source (or a firstterminal or the like) of a transistor is electrically connected to Xthrough at least a first connection path, the first connection path doesnot include a second connection path, the second connection path is apath between the source (or the first terminal or the like) of thetransistor and a drain (or a second terminal or the like) of thetransistor, Z1 is on the first connection path, the drain (or the secondterminal or the like) of the transistor is electrically connected to Ythrough at least a third connection path, the third connection path doesnot include the second connection path, and Z2 is on the thirdconnection path” and “a source (or a first terminal or the like) of atransistor is electrically connected to X at least with a firstconnection path through Z1, the first connection path does not include asecond connection path, the second connection path includes a connectionpath through which the transistor is provided, a drain (or a secondterminal or the like) of the transistor is electrically connected to Yat least with a third connection path through Z2, and the thirdconnection path does not include the second connection path.” Stillanother example of the expression is “a source (or a first terminal orthe like) of a transistor is electrically connected to X through atleast Z1 on a first electrical path, the first electrical path does notinclude a second electrical path, the second electrical path is anelectrical path from the source (or the first terminal or the like) ofthe transistor to a drain (or a second terminal or the like) of thetransistor, the drain (or the second terminal or the like) of thetransistor is electrically connected to Y through at least Z2 on a thirdelectrical path, the third electrical path does not include a fourthelectrical path, and the fourth electrical path is an electrical pathfrom the drain (or the second terminal or the like) of the transistor tothe source (or the first terminal or the like) of the transistor”. Whenthe connection path in a circuit structure is defined by an expressionsimilar to the above examples, a source (or a first terminal or thelike) and a drain (or a second terminal or the like) of a transistor canbe distinguished from each other to specify the technical scope.

Note that these expressions are examples and there is no limitation onthe expressions. Here, X, Y, Z1, and Z2 each denote an object (e.g., adevice, an element, a circuit, a wiring, an electrode, a terminal, aconductive film, and a layer).

Even when independent components are electrically connected to eachother in a circuit diagram, one component has functions of a pluralityof components in some cases. For example, when part of a wiring alsofunctions as an electrode, one conductive film functions as the wiringand the electrode. Thus, “electrical connection” in this specificationincludes in its category such a case where one conductive film hasfunctions of a plurality of components.

EXPLANATION OF REFERENCE

AF1: alignment film, AF2: alignment film, ANO: wiring, C1: capacitor,C2: capacitor, CF1: coloring film, CSCOM: wiring, G1: scan line, G2:scan line, GD: driver circuit, GDA: driver circuit, GDB: driver circuit,KB1: structure body, M: transistor, MD: transistor, M1: node, M2: node,P1: input position coordinate data, P2: sensing data, S1: signal line,S2: signal line, SD: driver circuit, SD1: driver circuit, SD2: drivercircuit, sel0: signal line, sel1: signal line, SS: control data, SS1:control data, SS2: control data, SS3: control data, SW1: switch, SW1B:switch, SW2: switch, V0: potential, V00: background data, V1: imagedata, V11: data, V12: data, VCOM1: wiring, VCOM2: wiring, 100:transistor, 102: substrate, 104: conductive film, 106: insulating film,107: insulating film, 108: oxide semiconductor film, 108 a: oxidesemiconductor film, 108 b: oxide semiconductor film, 108 c: oxidesemiconductor film, 112 a: conductive film, 112 b: conductive film, 114:insulating film, 116: insulating film, 118: insulating film, 120 a:conductive film, 120 b: conductive film, 200: information processingdevice, 210: arithmetic device, 211: arithmetic portion, 212: memoryportion, 214: transmission path, 215: input/output interface, 220:input/output device, 230: display portion, 230B: display portion, 231:display region, 232: pixel, 233: region, 235A: display element, 235B:display element, 239: selection circuit, 240: input portion, 250: sensorportion, 290: communication portion, 501C: insulating film, 504:conductive film, 505: bonding layer, 506: insulating film, 508:semiconductor film, 508A: region, 508B: region, 508C: region, 511B:conductive film, 511C: conductive film, 512A: conductive film, 512B:conductive film, 516: insulating film, 518: insulating film, 519B:terminal, 519C: terminal, 520: functional layer, 521: insulating film,522: contact portion, 524: conductive film, 528: insulating film, 530:pixel circuit, 550: display element, 551: electrode, 552: electrode,553: layer, 570: substrate, 591A: opening, 591B: opening, 591C: opening,700: display panel, 700B: display panel, 702: pixel, 705: sealant, 750:display element, 751: electrode, 751H: opening, 752: electrode, 753:layer, 770: substrate, 770P: functional film, 771: insulating film, 800:input/output device, 801: upper cover, 802: lower cover, 803: FPC, 804:touch sensor, 805: FPC, 806: display panel, 809: frame, 810: drivercircuit, 811: battery, 1189: ROM interface, 1190: substrate, 1191: ALU,1192: ALU controller, 1193: instruction decoder, 1194: interruptcontroller, 1195: timing controller, 1196: register, 1197: registercontroller, 1198: bus interface, 1199: ROM, 1200: memory element, 1201:circuit, 1202: circuit, 1203: switch, 1204: switch, 1206: logic element,1207: capacitor, 1208: capacitor, 1209: transistor, 1210: transistor,1213: transistor, 1214: transistor, 1220: circuit, 3001: wiring, 3002:wiring, 3003: wiring, 3004: wiring, 3005: wiring, 3200: transistor,3300: transistor, 3400: capacitor, 5000: housing, 5001: display portion,5002: display portion, 5003: speaker, 5004: LED lamp, 5005: operationkey, 5006: connection terminal, 5007: sensor, 5008: microphone, 5009:switch, 5010: infrared port, 5011: recording medium reading portion,5012: support portion, 5013: earphone, 5014: antenna, 5015: shutterbutton, 5016: image receiving portion, 5017: charger, 7302: housing,7304: display panel, 7305: icon, 7306: icon, 7312: operation button,7313: connection terminal, 7321: band, 7322: clasp.

This application is based on Japanese Patent Application serial no.2016-018553 filed with Japan Patent Office on Feb. 3, 2016, the entirecontents of which are hereby incorporated by reference.

The invention claimed is:
 1. An information processing devicecomprising: an input/output device; and an arithmetic device, whereinthe input/output device is configured to supply input positioncoordinate data and sensing data, wherein the input/output device isconfigured to receive image data and control data, wherein thearithmetic device is configured to receive the input position coordinatedata and the sensing data, wherein the arithmetic device is configuredto supply the image data and the control data, wherein the input/outputdevice comprises a display portion, an input portion, and a sensorportion, wherein the input portion is configured to supply the inputposition coordinate data, wherein the sensor portion is configured tosupply the sensing data, wherein the display portion is configured todisplay the image data, wherein the display portion comprises aselection circuit, a first driver circuit, a second driver circuit, anda display panel, wherein the arithmetic device is configured to generatethe image data, wherein the arithmetic device is configured to generatethe control data on the basis of the input position coordinate data, thesensing data, and the image data, wherein the control data is any of afirst-status control data, a second-status control data, and athird-status control data, wherein the selection circuit is configuredto supply the image data to the first driver circuit and background datato the second driver circuit in the case where the first-status controldata is supplied, wherein the selection circuit is configured to supplybackground data to the first driver circuit and the image data to thesecond driver circuit in the case where the second-status control datais supplied, and wherein the selection circuit is configured to supplythe image data to the first driver circuit and the second driver circuitin the case where the third-status control data is supplied.
 2. Theinformation processing device according to claim 1, wherein the displaypanel comprises a first signal line, a second signal line, and a groupof pixels, wherein the group of pixels are arranged in a columndirection, wherein the first signal line is electrically connected tothe group of pixels arranged in the column direction, wherein the firstsignal line is electrically connected to the first driver circuit,wherein the second signal line is electrically connected to the group ofpixels arranged in the column direction, and wherein the second signalline is electrically connected to the second driver circuit.
 3. Theinformation processing device according to claim 2, wherein the group ofpixels each comprise a first display element and a second displayelement, wherein the first display element comprises a reflectivedisplay element, wherein the first display element is electricallyconnected to the first signal line, wherein the second display elementcomprises a light-emitting element, and wherein the second displayelement is electrically connected to the second signal line.
 4. Theinformation processing device according to claim 3, wherein the firstdisplay element comprises a reflective film that reflects external lightin a display direction and is configured to control intensity of thereflected light, wherein the reflective film comprises an opening, andwherein the second display element comprises a region overlapping withthe opening and a layer containing a light-emitting organic compound andis configured to emit light toward the opening.
 5. The informationprocessing device according to claim 1, wherein the arithmetic device isconfigured to, when an icon is selected, supply the third-status controldata in accordance with coordinates of a region where the icon isdisplayed.
 6. The information processing device according to claim 1,wherein the arithmetic device is configured to determine a particularicon on the basis of a selection history of the icon and supply thethird-status control data toward coordinates of a region where theparticular icon is displayed.
 7. The information processing deviceaccording to claim 1, wherein the arithmetic device is configured tosupply the third-status control data toward a pointer display regionuntil a certain period of time has passed from the last input from theinput portion, and wherein the arithmetic device is configured to supplythe first-status control data or the second-status control data towardthe pointer display region after the certain period of time has passedfrom the last input from the input portion.
 8. The informationprocessing device according to claim 1, wherein the sensor portioncomprises an illuminance sensor, and wherein the illuminance sensor isconfigured to supply the sensing data comprising illuminance data on anenvironment where the information processing device is used.
 9. Theinformation processing device according to claim 1, wherein the inputportion comprises at least one of a keyboard, a hardware button, apointing device, a touch sensor, an illuminance sensor, an imagingdevice, an audio input device, a viewpoint input device, and an attitudedetermination device.
 10. An information processing device comprising:an input/output device; and an arithmetic device, wherein theinput/output device is configured to supply input position coordinatedata and sensing data, wherein the input/output device is configured toreceive image data and control data, wherein the arithmetic device isconfigured to receive the input position coordinate data and the sensingdata, wherein the arithmetic device is configured to supply the imagedata and the control data, wherein the input/output device comprises adisplay portion, an input portion, and a sensor portion, wherein theinput portion is configured to supply the input position coordinatedata, wherein the sensor portion is configured to supply the sensingdata, wherein the display portion is configured to display the imagedata, wherein the display portion comprises a selection circuit, a firstdriver circuit, a second driver circuit, and a display panel, whereinthe arithmetic device is configured to generate the image data, whereinthe arithmetic device is configured to generate the control data on thebasis of the input position coordinate data, the sensing data, and theimage data, wherein the control data is any of a first-status controldata, a second-status control data, and a third-status control data,wherein the selection circuit is configured to supply the image data tothe first driver circuit and black display data to the second drivercircuit in the case where the first-status control data is supplied,wherein the selection circuit is configured to supply black display datato the first driver circuit and the image data to the second drivercircuit in the case where the second-status control data is supplied,and wherein the selection circuit is configured to supply the image datato the first driver circuit and the second driver circuit in the casewhere the third-status control data is supplied.
 11. The informationprocessing device according to claim 10, wherein the display panelcomprises a first signal line, a second signal line, and a group ofpixels, wherein the group of pixels are arranged in a column direction,wherein the first signal line is electrically connected to the group ofpixels arranged in the column direction, wherein the first signal lineis electrically connected to the first driver circuit, wherein thesecond signal line is electrically connected to the group of pixelsarranged in the column direction, and wherein the second signal line iselectrically connected to the second driver circuit.
 12. The informationprocessing device according to claim 11, wherein the group of pixelseach comprise a first display element and a second display element,wherein the first display element comprises a reflective displayelement, wherein the first display element is electrically connected tothe first signal line, wherein the second display element comprises alight-emitting element, and wherein the second display element iselectrically connected to the second signal line.
 13. The informationprocessing device according to claim 12, wherein the first displayelement comprises a reflective film that reflects external light in adisplay direction and is configured to control the intensity of thereflected light, wherein the reflective film comprises an opening, andwherein the second display element comprises a region overlapping withthe opening and a layer containing a light-emitting organic compound andis configured to emit light toward the opening.
 14. The informationprocessing device according to claim 10, wherein the arithmetic deviceis configured to, when an icon is selected, supply the third-statuscontrol data in accordance with coordinates of a region where the iconis displayed.
 15. The information processing device according to claim10, wherein the arithmetic device is configured to determine aparticular icon on the basis of a selection history of the icon andsupply the third-status control data toward coordinates of a regionwhere the particular icon is displayed.
 16. The information processingdevice according to claim 10, wherein the arithmetic device isconfigured to supply the third-status control data toward a pointerdisplay region until a certain period of time has passed from the lastinput from the input portion, and wherein the arithmetic device isconfigured to supply the first-status control data or the second-statuscontrol data toward the pointer display region after the certain periodof time has passed from the last input from the input portion.
 17. Theinformation processing device according to claim 10, wherein the sensorportion comprises an illuminance sensor, and wherein the illuminancesensor is configured to supply the sensing data comprising illuminancedata on an environment where the information processing device is used.18. The information processing device according to claim 10, wherein theinput portion comprises at least one of a keyboard, a hardware button, apointing device, a touch sensor, an illuminance sensor, an imagingdevice, an audio input device, a viewpoint input device, and an attitudedetermination device.